that is my concern as well, if it truly was so widespread and useful I doubt they could turn a profit, however its real market is apparently much smaller than people suspect.

twitter simply cannot reach people who don't go looking for it, it would need to basically just randomly show up on your instant messenger unbidden, it has no universal connector like radio and tv which are everywhere.

then the last issue is there are too many voices on twitter so only those connected get out and assume importance. importance to only users of the medium