I wonder what percentage of people find conferences a means to really establish friendships with people, as you describe Steve. I have been to a handful of SQL Saturdays and met several people there, but would not remember them if I saw the the following year. Granted, I am pretty introverted and don't easily connect with people. Still, I wonder how many people would say these once-a-year events are effective for more than just adding a linked-in connection.
That's a good question. I would say a minority, though I would hope it's closer to half.
It takes effort, and making an effort to get to know people at events, user groups, etc. is part of an investment in growing your career and network. I meet lots of people, and I make an effort to chat with them. There have been many times I return to an event the next year and remember someone's face and chat again.