What about the chicken and egg problem?

What about it?

How do you intend to solve it? If few people are on your site, nobody treats reputation on it as a real reputation. If nobody treats it as a real reputation, nobody will come.

One way is to get NGOs to adopt it for their volunteers and to have volunteers get rep from people they help and or serve.

It's interesting, what PG would say. I would expect YCombinator to have many non-mainstream startups, but I don't know.