That may be so, but there are binary packages available. And while that is the case, they should be updated every so often. I mean, ffmpeg is almost 6 months old and it's tied to revision 14236 - the current revision is 16380! We are 2000 commits behind, it's astounding.
Not to mention I recently ran up into a bug where ffmpeg causes mpd to crash, and it's because the package is so out-dated. And there are other bug reports as well, dealing with other crashes and broken ogg support:
http://bugs.archlinux.org/index.php?string=ffmpeg&project=1So the question remains, will these packages be updated anytime soon?
Back to your point about it being difficult to package - while I realize there are resource implications to this suggestion, I think the goal would be to have a couple different binary packages available to hit the most common uses, like is done with some other packages. I wouldn't throw up my hands and resort to compiling from source. Any idea how long it takes to compile mplayer on a p3? Trust me, it's not fun.
Scott