Can online networking and web 2.0 technologies help with personal fitness?

Since it seems like we can’t bump old questions I will post this question again, since it was really poorly phrased last time. I hope this doesn’t annoy anyone.

I’m writing a paper on personal fitness combined with social networking and web 2.0 technologies – what I, and some others, call fitness 2.0. I need resources in the form of articles, blogs, etc. that can help me come to a conclusion. What I want to know is:

1. Can online social communities improve motivation and participation in regards to personal fitness and health. With fitness and health I mean working out, thinking about what you eat and such, in order to reach a better level of personal fitness.

2. What web 2.0 tools these communities use and can use to increase the socialization and motivation.

3. Why do these tools accomplish the above?

Even if you don’t know of any articles, blogs etc. about this, personal thoughts that might enlighten me on the matter are most welcome.

This is my research question, that I might rephrase soon, if it helps:
Can online social networking, via web 2.0 communities, benefit people’s exercise habits?

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Phrasing questions is truly an art… :)