Customers will care about controlling their data as soon as someone offers a useful product that requires it. Many are already reluctant to get involved with Facebook because of this.

http://www.joelonsoftware.com/articles/fog0000000052.html

As it is, MySpace users who want to switch to Facebook do it anyway, leaving behind a GhostSpace where they log into to check messages maybe once every 2-3 months. People are going to get sick of that crap, and will switch to a service that promises they'll never have to worry about it again.