I do not think that FB does helps effectively in finding their own identity. I agree with the comment by patrio84 that there are a lot of people who falsify their identity on facebook in order to receive acceptance or maybe merely for fun for them to "live" virtually, an escape for them, from the reality. I mean people are creating facebook account for their pets. (O_O)
I do think that facebook does provide a platform for one to experiment with different identity which they think they might be, but does not facilitate in depth understanding of oneself.
I still thinks that engaging with real people is really important for one to find their own identity. Internet may be a source for a person to get the information and where to look for help. Finding one's identity is not an easy path, sometimes I thinks that one can understand other people better than themselves. There are people who spend their life in search of who they are and what they want in life... The search is a journey...
I also believe that facebook is not a good place to form intimate relationship, but I have to say there is absolutely no possibility of it happening but just that the possibility is small. One is in a relationship with another is because of the way of how they feel towards each other. Their body gesture, their smiles, eyes contact when they talked, their facial expression and all others which are contributing factor to one's feeling towards another person, all these little things make you think that, "hey I like the way you smile when I said something funny...", which apparently cannot be "channeled" through facebook. Besides the sincerity and truthfulness of what is being said online is also one of the reason why I do not think that facebook is a place for the formation relationship. Apart from that, people might not even take the relationship that is form on facebook seriously due to the flexibility it provides, one can get into a relationship now and get out from it the next second without even telling another person, they can just simply disappear.