The sentence that follows the quote is "So unless you discover a competitor with the sort of lock-in that would prevent users from choosing you, don't discard the idea.". Most of the winners in the examples you gave had insurmountable lock-in (network effects, etc).

App.net lost to itself. I know of exactly one person who decided to pay money, and it's my friend who'd buy/try anything once.

Try to charge money in a space that's free, in return for..... I don't really know tbh, is a recipe for suicide. It may have worked in the 2 weeks of the novelty effect, and that's it.