I doubt you'd manage to get even 0.01% to pay for social networking. It would likely be more trouble than it's worth, compared to being advertising supported.
The only thing keeping people from paying $0.50 to remove ads and data mining is a system frictionless enough to let people do it easily. The cost is not in any way prohibitive. Make it a single click, and a barely noticeable $0.50 monthly charge and I think a lot of people would sign up.
I'm all in favor of micropayments, but we also have to keep in mind that if people pay, they could expect more service/customer care.
You're assuming they make less than $0.50/month out of those people from ads...
I wish I could find the source, but its documented somewhere on The Nets that this is roughly what they make– perhaps a bit less.