Work people on IM

Over the past few years, I've experienced different IM clients, from ICQ to Yahoo to AOL to MSN. During that time, as an employee at Amazon, if I ever wanted to chat with my co-workers, I had to add them to an internal Windows Messenger IM client (mainly because all other IM clients were blocked). As a result, the majority of my buddies on my MSN Messenger are actual, personal friends. Since joining Microsoft, I notice that a lot of people use MSN Messenger and I get requests often from co-workers for my MSN Messenger account name so they can add me to their buddy list. So I'm now moving into the territory where my IM experience is muddled with both personal friends and coworkers. Hmm. I guess I feel strange about it because I want to be able to sign into Messenger from home and not have coworkers see me go online. It's that feeling of being unattached from work--to be able to IM with friends and not feel like your coworkers are in the room too and can contact you as easily as your friends. I use Communicator at work, which works for most people. But what do I do with coworkers who ask for my MSN Messenger address? Do I give them my usual? Should I create another account and maintain that one? (which I'll likely never sign into?). I wish there was a feature where I could "hide" myself from a particular group of messenger buddies. Call me paranoid.