We all like our friends, but sometimes you just want to log in and get some things done without striking up a conversation. Sometimes you can be in a bad mood, have limited time, or just don't feel talkative. Heck, I'll be honest... sometimes you end up on the friend list of people you don't really want to talk to but are too polite to ignore.
Currently people can add you to a friend list and see when you are online and which server you are on. It would be nice to be able to log in anonymously or invisibly for times when you just don't feel up to chatting.
Even better, perhaps an option in settings as to whether your friends can even track you when you're online, so you can choose to opt out of being tracked by your stalkers... i mean, friends. ^_-
I do enjoy my friends, but there are times I like to be a private person. I think a lot of people can be like that. Some days you want to socialize, some days you just want to focus on your own thing.