When I've been over at my sisters and they have their good friends over, they sometimes talk about health issues openly (I feel kind of awkward being there). So I think, in my opinion, friendship involves trust that you can talk about something important to you without feeling that you are risking the friendship.
> A few years ago, I took a cross-country road trip with a guy that I met through a mutual friend.
Some of my best friends have been friends of friends. I meet someone and later on I meet one of their friends - and we bond quickly. By meeting more people, you geometrically expand your possibilities. Life is random. You're not going to hit it off with everyone - but the more people you "bounce" off of in your social universe - the better chance of a happy collision. Friendships can decay rapidly - but enjoy the times.
GrubWithUs brings in some planned serendipity.