The only part of gnome-media-2.32.0 that still uses libunique is gnome-volume-control, which we're not building. I've confirmed gnome-media-2.32.0-r300 builds without libunique installed, and it seems to end up with no reference to libunique in installed files if built with libunique present. The dependency should just be removed (after which on my system nothing else depends on libunique, and depcleaning packages makes me happy).
Fixed, thanks for noticing! > 13 May 2012; Alexandre Rostovtsev <tetromino@gentoo.org> > gnome-media-2.32.0-r300.ebuild: > Drop unneeded libunique dep (bug #415391, thanks to Marien Zwart).