It is unclear how the application got in this state but as a result it cannot be deleted.  The error in the log file:

Started DELETE "/broker/rest/domains/foobar/applications/sample" for 66.187.233.202 at Wed Apr 04 12:59:41 -0400 2012
  Processing by ApplicationsController#destroy as JSON
  Parameters: {"id"=>"sample", "domain_id"=>"foobar"}
Response from Streamline took (/wapps/streamline/login.html): 478.72 ms
POST Response code = 200
Current login = xcoulon+test / authenticated for xcoulon+test
Adding user xcoulon+test...inside authenticate
MongoDataStore.find(CloudUser, xcoulon+test, xcoulon+test)

MongoDataStore.find(CloudUser, xcoulon+test, xcoulon+test)

Deleting application sample
DEBUG: DYNECT Login with path: /REST/Session/
DEBUG: DYNECT Response: {"status": "success", "data": {"token": "dvViHwHGnC4pn4Z/hqiUnk5yx5PLSSCbTrbwPWP7B9Jd1MY0nTzKfeK/22VZoIXrPIVeZXyPhLcGdJv5UklSg4VdYL91XmU2aAr9VL9kPd8lA7+FcBF1Afvl/kJpkls6g8wTmSyG/DGwNHdzcc8pVAmoux1NvozK", "version": "3.3.2"}, "job_id": 83285140, "msgs": [{"INFO": "login: Login successful", "SOURCE": "BLL", "ERR_CD": null, "LVL": "INFO"}]}
DEBUG: DYNECT Response data: tokendvViHwHGnC4pn4Z/hqiUnk5yx5PLSSCbTrbwPWP7B9Jd1MY0nTzKfeK/22VZoIXrPIVeZXyPhLcGdJv5UklSg4VdYL91XmU2aAr9VL9kPd8lA7+FcBF1Afvl/kJpkls6g8wTmSyG/DGwNHdzcc8pVAmoux1NvozKversion3.3.2
DEBUG: DYNECT delete with path: /REST/CNAMERecord/rhcloud.com/sample-foobarbaz.stg.rhcloud.com/ and headers: {"Content-Type"=>"application/json", "Auth-Token"=>"dvViHwHGnC4pn4Z/hqiUnk5yx5PLSSCbTrbwPWP7B9Jd1MY0nTzKfeK/22VZoIXrPIVeZXyPhLcGdJv5UklSg4VdYL91XmU2aAr9VL9kPd8lA7+FcBF1Afvl/kJpkls6g8wTmSyG/DGwNHdzcc8pVAmoux1NvozK"}
DEBUG: DYNECT: Could not find /REST/CNAMERecord/rhcloud.com/sample-foobarbaz.stg.rhcloud.com/ to delete
DEBUG: DYNECT put/post with path: /REST/Zone/rhcloud.com/ json data: {"publish":"true"} and headers: {"Content-Type"=>"application/json", "Auth-Token"=>"dvViHwHGnC4pn4Z/hqiUnk5yx5PLSSCbTrbwPWP7B9Jd1MY0nTzKfeK/22VZoIXrPIVeZXyPhLcGdJv5UklSg4VdYL91XmU2aAr9VL9kPd8lA7+FcBF1Afvl/kJpkls6g8wTmSyG/DGwNHdzcc8pVAmoux1NvozK"}
DEBUG: DYNECT Response: {"status": "success", "data": {"zone_type": "Primary", "serial_style": "increment", "serial": 547296, "zone": "rhcloud.com"}, "job_id": 83285148, "msgs": [{"INFO": "changeset: No changes to apply.", "SOURCE": "BLL", "ERR_CD": null, "LVL": "INFO"}, {"INFO": "publish: Could not publish rhcloud.com. No changes to apply.", "SOURCE": "BLL", "ERR_CD": null, "LVL": "INFO"}]}
DEBUG: DYNECT Response data: serial547296zone_typePrimaryzonerhcloud.comserial_styleincrement
DEBUG: DYNECT delete with path: /REST/Session/ and headers: {"Content-Type"=>"application/json", "Auth-Token"=>"dvViHwHGnC4pn4Z/hqiUnk5yx5PLSSCbTrbwPWP7B9Jd1MY0nTzKfeK/22VZoIXrPIVeZXyPhLcGdJv5UklSg4VdYL91XmU2aAr9VL9kPd8lA7+FcBF1Afvl/kJpkls6g8wTmSyG/DGwNHdzcc8pVAmoux1NvozK"}
DEBUG: DYNECT Response: {"status": "success", "data": {}, "job_id": 83285155, "msgs": [{"INFO": "logout: Logout successful", "SOURCE": "BLL", "ERR_CD": null, "LVL": "INFO"}]}
DEBUG: DYNECT Response data: 
DEBUG: Deconfiguring embedded application 'mongodb-2.0' in application 'sample' on node 'ex-std-node1.stg.rhcloud.com'
DEBUG: Sending to Nurture:application: app_uuid='5229a2c0f1424aed90d4ca8f20c0f9a2' action='deconfigure'
0
DEBUG: Wed Apr 04 12:59:45 -0400 2012 Sending to Apptegic:application: user='xcoulon+test' app_uuid='5229a2c0f1424aed90d4ca8f20c0f9a2' action='deconfigure'
DEBUG: Wed Apr 04 12:59:45 -0400 2012 Done sending to Apptegic
DEBUG: rpc_exec_direct: rpc_client=#<MCollective::RPC::Client:0x7fea088e7070>
DEBUG: rpc_client.custom_request('cartridge_do', {:action=>"deconfigure", :args=>"'sample' 'foobarbaz' '5229a2c0f1424aed90d4ca8f20c0f9a2'", :cartridge=>"embedded/mongodb-2.0"}, @id, {'identity' => @id})
DEBUG: [#<MCollective::RPC::Result:0x7fea08c90de8 @agent="libra", @results={:sender=>"ex-std-node1.stg.rhcloud.com", :statusmsg=>"cartridge_do_action failed 125.  Output sample.  Application directory doesn't exist:  /var/lib/stickshift/5229a2c0f1424aed90d4ca8f20c0f9a2/sample\n", :data=>{:exitcode=>125, :output=>"sample.  Application directory doesn't exist:  /var/lib/stickshift/5229a2c0f1424aed90d4ca8f20c0f9a2/sample\n"}, :statuscode=>1}, @action="cartridge_do">]
DEBUG: server results: sample.  Application directory doesn't exist:  /var/lib/stickshift/5229a2c0f1424aed90d4ca8f20c0f9a2/sample
DEBUG: rpc_exec: Filtering rpc_exec to server ex-std-node1.stg.rhcloud.com
DEBUG: rpc_exec: rpc_client=#<MCollective::RPC::Client:0x7fea08c881c0>
Node execution failure (invalid exit code from node).  If the problem persists please contact Red Hat support.
#<StickShift::NodeException: Node execution failure (invalid exit code from node).  If the problem persists please contact Red Hat support.>
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`run_callbacks'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/abstract_controller/callbacks.rb:17:in `process_action'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal/rescue.rb:17:in `process_action'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal/instrumentation.rb:30:in `process_action'", "/usr/lib/ruby/gems/1.8/gems/activesupport-3.0.10/lib/active_support/notifications.rb:52:in `instrument'", "/usr/lib/ruby/gems/1.8/gems/activesupport-3.0.10/lib/active_support/notifications/instrumenter.rb:21:in `instrument'", "/usr/lib/ruby/gems/1.8/gems/activesupport-3.0.10/lib/active_support/notifications.rb:52:in `instrument'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal/instrumentation.rb:29:in `process_action'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/abstract_controller/base.rb:119:in `process'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/abstract_controller/rendering.rb:41:in `process'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal.rb:138:in `dispatch'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_controller/metal.rb:178:in `action'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_dispatch/routing/route_set.rb:62:in `call'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_dispatch/routing/route_set.rb:62:in `dispatch'", "/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_dispatch/routing/route_set.rb:27:in `call'", "/usr/lib/ruby/gems/1.8/gems/rack-mount-0.7.1/lib/rack/mount/route_set.rb:150:in `call'", "/usr/lib/ruby/gems/1.8/gems/rack-mount-0.7.1/lib/rack/mount/code_generation.rb:93:in `recognize'", "/usr/lib/ruby/gems/1.8/gems/rack-mount-0.7.1/lib/rack/mount/code_generation.rb:75:in `optimized_each'", 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"/usr/lib/ruby/gems/1.8/gems/railties-3.0.10/lib/rails/application.rb:168:in `call'", "/usr/lib/ruby/gems/1.8/gems/railties-3.0.10/lib/rails/application.rb:77:in `send'", "/usr/lib/ruby/gems/1.8/gems/railties-3.0.10/lib/rails/application.rb:77:in `method_missing'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/rack/request_handler.rb:96:in `process_request'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_request_handler.rb:514:in `accept_and_process_next_request'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_request_handler.rb:274:in `main_loop'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/classic_rails/application_spawner.rb:321:in `start_request_handler'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/classic_rails/application_spawner.rb:275:in `send'", 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"/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/spawn_manager.rb:219:in `spawn_rails_application'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/spawn_manager.rb:214:in `spawn_rails_application'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server_collection.rb:82:in `synchronize'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/spawn_manager.rb:213:in `spawn_rails_application'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/spawn_manager.rb:132:in `spawn_application'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server.rb:357:in `__send__'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'", "/usr/lib/ruby/gems/1.8/gems/passenger-3.0.4/helper-scripts/passenger-spawn-server:102"]
MongoDataStore.save(Application, xcoulon+test, sample, #hidden)