My Suggestion:
I've noticed you're able to add just about any username to your Friends list.
Even if that username is not Created, but it will add it to your Friends list.
My Suggestion is to only add usernames that Exist other then usernames that do not Exist.
I had been waiting 2-3 days for a friend of mine to log on, he would always tell me he's online.
What happened was i misspelled his username.. and it Added a Random Username.
Thanks.
-Pro