I think a lot of people define a lock-in as a monetary lock-in. You can't leave without spending X dollars to terminate early.

But given the time to re-do a large portion of your data on FB (assuming you've used it a fair amount, as many people on it do), at minimum wage, it's probably nearly as "expensive" to leave FB as to switch cell phone providers.

I know it's not a 1-to-1 comparison at all, and I've deleted my account and felt no loss. But my use of FB was incredibly minimal compared to most of my friends who are on it, and I hear "I hate Facebook, but everyone is on it" echoed from nearly everyone I encounter.