I only ask people at knife and gun shows, and people I know. Never had an experience like Tony's, but most people, when they realize that a fat grizzly bear sized man has just asked them what kind of knife they have, get unnerved a little bit. If you were carrying an expensive knife, from a Chris Reeve/Strider to a Benchmade/Spyderco/ZT, and you were asked about it, would you think you were about to get robbed/attacked?
I do ask non knife nut friends and family about their knives, and have gotten to see some interesting knives.