I sympathise with the sentiment expressed but must point out that there is no market force that prefers un-established open products to established walled gardens save for a fraction of hackers' tastes and preferences. Most people don't care, for rationally self-interested reasons, whether the product they use is open or closed as much as whether it works or not.
I'm not predicting that Wordpress will supersede Facebook, but I do predict that something will eventually. Of all the alternatives known to me, Wordpress is a fascinating suggestion.
1) The existing platform being annoying/uninteresting/distrusted. 2) A small but "cool" section migrating to a new platform.
Facebook won by being adopted by an effective wedge group - college student. Those who open source might (or might not) be a different but effective wedge group.
Oh, yes there is, it's called change.
Closed systems overturn open systems just as much as the other way around (or closed v closed or open v open). Very few people outside hacker culture care whether what they use is open or closed.