If eject is not installed, then the 'eject' item in a CD-ROM context menu will unmount the cd, but it will not eject it.
This does not really break things, but does impair functionality. I'm not sure here. I have the same problem with ogg123, if ogg123 isn't installed it won't preview oggs on mouse-over. Is it really necessary to add this ? Let me ponder on this a bit.
Perhaps this is the sort of thing that can be controlled by the USE variable. ie. If oggvorbis is not in the USE list, then don't depend on ogg123. Not sure what you would do with eject though.
I think eject is small enough for it to be added as a non-optional dependency.
I added eject for now and vorbis-tools btw.