brilliant game, but there's not enough player-to-player interaction to call it a MMO. even for a "lite" MMO. A marketplace (with stuff to trade, erm ...) would be great. Be able to explore aetheria in coop would be nice, too.
got an idea for you, AdamAtomic and DannyBstyle.
use all 26 letters of the keyboard for the jump (the height and lenght of the jump would be exactly the same as it is now), but EACH letter would do a DIFFERENT air-trick.
maybe this idea dont fit with the canabalt "mood", but ... i think it would be awesome.
 "Monsters' Den: Book of Dread")
 "Project Wasteland 0")
 "Remnants of Skystone")
 "Kongai")
 "Sonny 2")
 "Competitive Line Waiting")
 "Canabalt")
 "Enigmata")
 "The Gun Game")