I met someone who went to my university who went to high school with Mike Grella (played for Leeds, not sure where he is now). Apparently he wasn't that good and was an *******. My dad was good friends with someone who played semi-professionally in the states and made a few appearances with the national team (this was before the MLS). I went to school with a professional basketball player and my brother was friends with a few very good college gridiron football players who might go pro.
When I was in Argentina I met two youth players. I went drinking with a group of guys in Rosario and one of them played for one of Newell's youth teams. Also, when I was at the Iguazu waterfall I met a youth player for Racing, a defender, I think his name was Richy something.
I'm surprised though that so many people here know professional football players...maybe it's because the UK is a (relatively) small country?
Also, I got my picture taken at the 2006 World Cup with Georges Bregy (Swiss star back in the 80's and 90's). Had no idea who he was but my friend's Swiss cousins immediately had us take a picture with him.
Also, the thought just occurred to me, do you think there is anyone famous on FM? I mean, I'm sure a few managers and players play this game (Wenger said he used it to scout players), and this is pretty much the most popular site for it...so it wouldn't surprise me.