Having lived in equatorial Africa for a decade, and having spent weeks driving to cross a single given country, I always get a kick of out conversations where someone asks, "Oh, you lived in Africa--did you know So-and-so?"
But sometimes, you do know them, and it's like HOLY SHIT SMALL WORLD. I was on a subway in Paris one night with two friends. A group of (American) girls heard us speaking english, we got to talking, they found out where I went to school (Penn State, huge effin uni), and were like "do you know so and so". Turns out so and so was my roommates ex-girlfriend. Small world, eh?
As a Brit holidaying in the States, I have been asked many many times in the most serious of tones if I know Prince Charles/the spice girls/David Beckham. Quite bizarre.
I get asked that all the time. But I'm from Iceland. With only a population of 300.000 it's to be expected. Funny thing is I've actually known the person twice when asked (but it's out of hundreds of queries).