Some good points made here, but I think the gloom and doom is a little overstated.

Facebook went through the same thing for awhile and then created facebook lite, then rolled more simplicity back into their main app.

A company like twitter is going to have a hard time pleasing everybody, and has to figure out the boundaries with its APIs as time goes on. In UI rate limits? They are probably battling spammers gaming the regular frontend like crazy, and are still hammering out the kinks for the real users.

As far as Dick Costollo goes, if there is anyone who I think would be pretty adept about balancing core ideals, while actually making money, he seems like the guy.