I've had a beer or at least met with several people I'd played a PC game with, and had a beer with another guy since we both contribute to the same music website. Forums exist in those scenarios but aren't the sole connection. There's one guy I met after talking to him on Facebook, but it was more of an interview thing as he was using the topic of metal to write for a university assignment.
I've also met a lot of people at concerts/live shows who I'd already communicated with online via local music forums, Last.fm or Facebook. But I wouldn't count those as meet-ups - I was already going to the shows anyway to see some band or maybe even their band, but it didn't really matter whether I found a chance to talk to them or not as that wasn't the point of going.