module-init-tools is compiled with --enable-zlib, even on fedora, so it's possible for a sysadmin to compress all the /lib/modules/..../FOO.ko files and still have modprobe etc. work. But elfutils won't find .ko.gz files during its search of offline modules, so systemtap wouldn't be able to probe them. Please consider extending libdwfl/linux-kernel-modules.c to look for .ko.gz files too.
This would entail too pieces of work. The easy one is making the .ko search look for .ko.gz too. The more complex one is teaching libdwfl to use libz to decompress into memory when using elf_begin. That is doable, and easier with consolidation of file-opening that the .sharing branch has. Seems like we could have it, but not a top priority real soon.
Implemented upstream, should be in 0.139
elfutils-0.139-1.fc10 has been pushed to the Fedora 10 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with su -c 'yum --enablerepo=updates-testing update elfutils'. You can provide feedback for this update here: http://admin.fedoraproject.org/updates/F10/FEDORA-2009-1005
These bugs are fixed in current Fedora 10/11 updates of elfutils.