It's actually a good idea... it would stop the spamming of "Are you there? I know your there. It says it in Who's Online huuuuuur." and the auto-AFK would help if someone went to do something thinking it wouldn't take long when in reality it's gonna take them a while and they didn't put up the AFK sign.
Wasn't that better if there who is in afk has (AFK) in back of their name if u push "Who". Like: Tammer (AFK) And if u are away over 10 min then u go afk and back of your name comes (AFK) too.