That might work out well for Facebook. I don't know what percentage of their user base would care enough to do so, though. And at this point, with all of the ridiculous things that have happened with their privacy, it might even seem extortive to me. It's one thing to tell everyone their stuff is public unless you pay from the beginning, but publicizing what one would otherwise assume to be private data late in the game and then charging to reprivatize would be underhanded.

As a customer, I'm actually a fan of the idea. If you aren't paying for something, you are generally the product not the customer (see: http://www.information-age.com/channels/security-and-continu...). If I willingly become a customer, then I don't have to be a product anymore. I like that option.

That is exactly how github works, too: https://github.com/plans

Link to Prezi signup: http://prezi.com/profile/signup/

Sounds good to me - I don't want to listen to all the fuss about privacy, let alone pay for it.