Many FT airline boards, and hotel boards, have a thread specifically to arrange such meet-ups. There are some off site boards for the same reason - look at my strap line for a hint as to my feelings about this ;)

I take the view that a fellow FTer who you have not previously met is no different from a casual acquaintance of a friend who we might meet for the same purpose. After all we have the same hobby in hanging around here!!

I have met a few FT folks and guested them into the lounge, and met others in the hotel courtesy coach and by casual chat realised we were going the same way and done the same - an opportunity to be friendly and pass some time when hanging around an airport is not to be missed.

Once I got to talking to my seatmate about travel and he mentioned he was going to the Presidents Club when we got to Houston. I managed to ask enough of a leading question (something like "is it nice?") so he asked me. Beyond that I'm a bit too shy about asking people on their way in to guest me. I don't think it's bad form though. I often guest people in to lounges if I get the chance so they don't have to feel shy like I do about asking :D