Just heard some exciting news, and wanted to pass it on...
A recent Disney guest had lunch at the Crystal Palace, in the Magic Kingdom, and mentioned that some of the food items on the buffet were marked as either "vegetarian" or "vegan". He didn't take any pictures, and isn't sure of specifics, but he's positive that the notes were there. (This guest was neither a vegetarian, nor a vegan. He probably never would have mentioned it, except that I think he was a bit surprised to discover that a dish marked "vegan" was actually quite tasty.)
This is very exciting news. I am absolutely positive that there were no such notes in December 2009. (I *did* take pictures, and notes, and being a vegan, most definitely would have noticed.) While I really don't know if the vegan options are any better than before, clear signage is a huge step in the right direction. While I have always managed to get a chef to walk through the buffets with me, and point out the vegan options, some are more thorough than others, and sometimes it's just difficult to remember everything. (As I actually had a rather unpleasant experience at Crystal Palace, I'm especially glad to hear of this improvement at this location.)
I have yet to hear of such signage at any other buffets, but I will certainly be on the lookout during my next visit. Let's hope this is a "sign" of things to come! :-)