Actually, I meant it as a small team or solo. Most of my mentor relationships starts with someone saying a clever thing on Facebook/Twitter/HN, a radio show, a random community, someone who wrote a book I learned a lot from, a tech talk somewhere.
It's similar to dating. Everyone prefers to be passive and matched to someone, or just bump into someone serendipitously. But it's easier to just muster the courage to talk to the next person on your mind. And they usually get flattered when asked for help as well, as long as it's not Bill Gates or anyone too far above your level.
Speaking of Bill Gates, there's a bit of anecdote from the Bill Gates documentary. At one point he met with Buffett and Buffett just kept asking questions like, "Why couldn't IBM beat Microsoft?" Bill was waiting for someone to ask him a question like that but nobody ever did. That's how mentor relationships are formed.