From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3)
Description of problem:
Epiphany should warn on browser close if multiple tabs are open.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
That was an upstream decision. If you search on bugzilla.gnome.org you
will probably find a closed bug about it.