I find smaller groups very useful. For example I'm hiring at the moment and I've directly approached some people I don't know personally who are in groups that

I find smaller groups very useful. For example I'm hiring at the moment and I've directly approached some people I don't know personally who are in groups that are small and represent (for me) a type of hacker I want to hire. The groups are less useful when large, but when small they can offer a way to locate people who could be perfect for you (and you for them).