I can't help but feel the ffmpeg guys, despite providing a great service to the world, have got a real chip on their shoulder when it comes to all things Ogg and Xiph.They don't like things that are badly designed. This same chip applies equally to a lot of other stuff, especially proprietary formats, like the utterly atrocious and buggy RealVideo 10.
Xiph gets a double dose, however, because of the methods that Xiph uses to market their bad technology. They have at times posted outright lies about their software and then, once proven wrong, often refuse to recant. Example: the Theora vs x264 PSNR comparison where they "accidentally" performed measurement wrong, making x264 appear 2x worse.
They use the same techniques as many of the more evil commercial companies out there, which annoys the hell out of people who disagree with such techniques. ffmpeg devs believe that open source should be about honesty and good technology, not lies and FUD. Xiph disagrees, believing that "the ends justify the means", creating a practically unbridgeable gulf.
Thus Xiph has spent the last few years spreading absurd amounts of FUD about everyone who they believe opposes them. They have managed to convince a shocking number of people that "ffmpeg is illegal" and that you should use their software instead. Ironically, almost all the FUD in the multimedia space in recent years has come from people who claim to support "free software"! Didn't we spend years criticizing Microsoft for the exact same thing?
And you wonder why people don't like them!