Of course, behavior models are only getting better, and the cost of network infrastructure is dropping every day. A point will eventually be reached where such a service becomes commercially viable. The trends allowing behavior models to get more accurate and useful and network architecture to get cheaper won't grind to a sudden halt when this point is reached, just like they didn't grind to a halt when targeted advertising became good enough and storage cheap enough for Google to profitably launch its free webmail service. Google's profits from each GMail user undoubtibly have continued to grow since the launch date. Has the value they're providing to their users grown at the same rate?

If it wanted to, Google could make Gmail a pay-to-use service at any time. But once Google has your personal information, you can't take it back or stop the company from using it in ways you never imagined when you 'freely' gave it away in exchange. With a few specialized exceptions, American law currently offers no rights to control how your personal information is used once it is collected. If you really want a marketplace where privacy can be commoditized fairly, you need to first set up a legal regime where sellers can control what they are offering to the same degree that buyers already can.

-- AndreiVoinigescu - 17 Dec 2008