Nintendo World Report examines what Brawling online is like.
The more troubling problems with friend matches seem to be related to friend code registration. Just like other online multiplayer Nintendo games, players who wish to buddy up online must exchange 12-digit friend codes and input them on each others' consoles. Once Nintendo Wi-Fi Connection detects that both users have added each others' Friend Codes, the registration process complete and you'll be able to see when your friends are on and jump into matches with them. Up until that point, the friend's name and number show up on the friends' list with the text "Awaiting Registration."

There seems to be a recurring trend with the registration process. Even when two people have registered each other, the two will sometimes not move beyond the Awaiting Registration stage. The situation has become a bit of a recurring joke on Radio Free Nintendo, the Nintendo World Report podcast.
Excerpted from Radio Free Nintendo: Episode 92
Excerpted from Radio Free Nintendo Episode 94
NWR Reviews Editor Jon Lindemann, who spoke of his problems in the clip from RFN Episode 92, elaborated on his problems with friend codes in Brawl.
"The friend codes are annoying in the first place, but on top of that they don't even work. Not even half of the 17 people I have added have gotten past the 'Awaiting Registration' phase. [NWR Contributing Editor] Jonny Metts has me added on his end and I show up as registered on his side, but he's still in "Awaiting Registration" on my side. But what's comical is that he can send me match replays and custom stages...but he's still in 'Awaiting Registration.' It's idiotic."
Like with all things in Smash Bros. Brawl, the problems registering friends do not affect everyone. There are plenty of people out there who have been able to add their friends and play games without any major incident. However, considering how smooth the online experience is in third-party Wii and Nintendo DS games, and especially how well things work on other consoles, it may be a case where Nintendo bit off more than it could chew when it comes to supporting the online feature set and the number of people wanting to play the game online, particularly in what will most likely be one of the best-selling, if not the best-selling, games of the Wii generation. While things are looking better now, you don't get a second chance to make a first impression.