I don't really talk about it, but most of the people I know have a sense for my special interests. A lot of times my special interests become productive and I talk about them alot, spend countless hours on them, and more often than not never finish them. I did finish one though, was a website, and hit up 70k hits/day for awhile. I wasn't impressed, but many of whom I told about it were rather impressed.
Alot of my friends label me as one who "starts projects but doesn't finish anything".
It's hard to hide them for me. I mean, when you spend 80 hours a week on something it tends to get noticed by people. My brother and I are pretty close so he knows, and since he knows, and all his friends are my friends, they usually know as well.
I'm not embarassed by it though. It's just me being me.
My special interests very from month to month though.