What do you think of contacting exs on things like Facebook, Myspace, etc?

What do you think of contacting exs on things like Facebook, MySpace, etc? I was messing around on Facebook and found my ex from atleast 6 years ago, and I've been considering sending him a message, just to say hi, see how his life is going. He lives half way across the country, and I have no interest in rekindling a romnace. But, he's one of the few exs I have that I left on good terms (He got out of the marines and moved back home and we lost touch) I told my boyfriend about it, and he said he doesnt care if I send him a message to say hi or anything like that. I've never done anything like this, and I'm wondering if it's normal to send a message to someone after 6 years. (He couldnt have found me because I dont use my real name.) Should I or shouldnt I and whats your opinion about the whole thing??