Mashable today is reporting on a USC Annenberg School of Communications study that concludes (among other things) that exactly 0% of Americans would be willing to pay for Twitter.
It seems like an obvious conclusion - that no one would be willing to pay for something that they value at "free."
Mashable makes and interesting comparison to the resistance to pay for news content on-line, which is a very different situation. Traditional news outlets, particularly the higher-quality ones, have historically charged for their service: we paid for newspapers (the physical versions) and the on-line content was an after-thought. Now that the on-line content is the primary access venue and the paper versions are fading quickly (more slowly for the higher-quality outlets, but still fading quickly), the access models have to change also.
Anecdotally, it's not hard to see that there is value in something that once carried a price, but is now free. Similarly, there is no value attached to something which has always been free. Meaning, it makes more sense that we'd pay for the New York Times on-line, but not for Twitter (or, for that matter, for Mashable).
So the acute sense of the obvious shows up again: the question isn't whether we'd pay for Twitter, but what Twitter can offer that would be worth paying for? Given Twitter's model of outsourcing nearly every additional feature and function to third-party services, can they be creative enough to create something that makes us say "wow - that's really worth the $9.95 per month!?"
I'm sure we'll see that in Mashable as well.