If it has real value, it should be able to simply charge for using it. If users are unwilling to pay (no matter how little) then it's clearly not that valuable to them. If they move to something like identi.ca, and it manages to maintain a reasonable service level with negligible costs (distributed servers, open source dev modle), then that's a better solution.

"If Twitter fails to find a revenue model and hits the deadpool, it will have a chilling effect on innovation" - please. I believe I recall some innovation in pre-Twitter era and I'm pretty sure there it will continue after it as well.