When I actually used my facebook, the only situation where I asked people for theirs was if I didn’t expect to meet them again
What kind of circumstances did you do that in? Meeting people at conferences? Or something else?
Meeting people in public and enjoying talking to them in general. Giving out my phone number might encourage people to call me, which I didn’t want to do since talking on the phone is almost impossible for me, and my IM screen names and emails at the time were too connected to my online personas for me to be comfortable mixing them with people who knew who I was in real life. Facebook was a real-life-friends-only venue that was entirely text-based, so I’d ask for a Facebook in the place that I might have asked for other contact information.
At this point, I no longer use Facebook because it’s my opinion that their total lack of ethics and tendency to sell content posted by users to advertisers make it uncomfortably risky, but I never had a bad reaction to asking under those circumstances.