Is there any evidence that people who post pictures or constant statuses of themselves (e.g. facebook, gonewild) have low self-esteem?

There seems to be a prevailing a view that individuals who post a lot have low self-esteem, in that they are seeking approval of others. This seems especially true for those that post scantily clothed/naked pictures of themselves.

I think the opposite could be true, in that those who post a lot, have the confidence to 'put themselves out there.'

I'm wondering what the evidence says about this question. Thanks!