I wondered about this myself, but I was thinking more about using it with Kinect. pretty hard to play any games standing in front of the projector.
anyway, I don't know if there's any major disadvantage to the short throw method(maybe loss in contrast from the optics?) but I have seen any home theatre oriented projectors made with a short throw. so at present time, you'd be stuck with a business projector, which means likely very bright, reduced contrast, and higher black levels.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1130K, 7.1/5.1.2 audio
Sources: HTPC(Enby), PS3, XBOX360, Wii
Control: Harmony One