Whether you enable or disable that useflag, bonjour is always disabled. The problem is in libgphoto2_port/configure.ac:164: with_bonjour=no This overrides the value passed on the command line to configure.
+*libgphoto2-2.4.7-r2 (07 Jan 2010) + + 07 Jan 2010; Gilles Dartiguelongue <eva@gentoo.org> + libgphoto2-2.4.3.ebuild, -libgphoto2-2.4.4.ebuild, + -libgphoto2-2.4.5.ebuild, +libgphoto2-2.4.7-r2.ebuild, + +files/libgphoto2-2.4.7-extra-dist.patch, + +files/libgphoto2-2.4.7-no-test-build.patch, + +files/libgphoto2-2.4.7-respect-bonjour.patch: + Fix USE=bonjour behavior, bug #283332. Do not build tests if not needed, + bug #226241. Add examples USE flag. Remove unwanted files for + /usr/share/doc. Clean up old revisions. For some odd reason I though this code worked perfectly fine in other configure.ac. Fixed in 2.4.7-r2. Thanks for reporting.