Is it weird to add someone on Facebook who I don't know well?

[Alice]

There's this guy I'm kind of talking to that has a friend who added me on WoW and he talks to me almost every time he gets online, only short conversations though. I've seen him face to face once a couple weeks ago and he seemed pretty cool, of course I'm not planning on trying to be more than friends with him or anything, I'd just like to get to know him better as a friend but I'm afraid adding him on Facebook would send the wrong signals/be a tad creepy? I found his Facebook because he posted on someone's wall and I already knew his name if that matters.. I may be overthinking it, but I'd just like to know if that would be considered creepy if I did? Might I add, the guy I'm talking to doesn't seem to mind that I talk to his friend considering he's the one who asked me to add him on WoW.