I met people through a baseball site I was a member of in the late 90s. It was basically the same thing as here, except we were baseball fans, met up to go to games, and didn't have to line up for nearly as long.
The first people I met through the site, I was still with my ex at the time, and he came with me. Just a few months after we split up, these friends from the site, this one married couple and a guy on his own (married though, devoted to his wife, but alone for the trip) came to Toronto to see a game and insisted I go with them. The were driving from Ohio, and came to pick me up at my house. I still remember my mom when they were picking me up. She was convinced that I'd be raped/murdered.
I went with them and had the most amazing time ever, and came back safely a few days later. I haven't been in touch with any of them for ages, but I'll always remember that - it was during a very low point for me, and they were fantastic company and so, so nice.
You just have to use common sense. The website was a community, much like this one, and although I had not met any of them, I knew other people on the site that had, and all of those people only had amazing things to say about them, so I felt very safe going off on my own with them.
I actually went on another trip with people from that site - two guys, and the three of us shared a hotel room.
Had an amazing time.There was some very bizarre romantic triangle drama, which was nuts and funny and makes me laugh to this day, but I had so much fun.