[fkdjs]

There are two barriers to entry: the network effect, s.t. the utility I derive corresponds to the friends I have on the social network, and their utility derives partly from me being on the social network, so at a critical mass it's hard to justify going onto another social network.

The network effect kicks in at a certain critical point. If you created a really compelling social network and added the feature s.t. people could say, "import from facebook", choosing your facebook login/pw, then if enough people did this, critical mass would be reached. The network effect just states that this critical mass might take awhile to reach, but it's not impossible. Facebook disallowing you from exporting your data makes it so competing networks cannot reach that critical point quickly enough.