I don't think the amount of people who would pay Twitter is that high.

In that case, Twitter is a dead duck. If Twitter isn't worthwhile spending money on, I can't see how they can operate as a profitable business.

Pay twitter for what? To read messages? Or to get their message out?

Start charging the folks (businesses, media et cetera) that have a million+ followers, these entities can surely pay to get their microblog posts published.

I don't think they could collect anything more than pocket money by merely charging > 1M accounts.

The amount of people who pay for Linkedin is considerably smaller.