I remember a guy once sent me a message saying I sucked (not sure if this was Trials or COD).
Replied back saying 'Thank you' or something like that, he sent me a FR after that.
The only FR I have ever declined (oh and Starfire's).
For the most part I accept friend requests, even if they're random.
If I know the name from the forums I am more likely to accept.
I do like it if the person sends me a message, but I think the only person who ever did that was my boyfriend.
Personally, I don't send out random friend requests 'cause I don't like to be rejected.