Maybe you got some stray clicks and accidentally clicked the 'buddy' icon? It's happened to me too.
I personally don't even know what the buddy list does... I added people to test it out, but it doesn't seemt to do that much. Then again, I always learn new things around this place. Anyone wanna fill me in?
The buddy list shows you who of your buddies are online in the user panel. Otherwise you can use it to pm more people at the same time. It's meant as a quick reference to the people you communicate with the most, so you don't have to remember the spelling of their usernames (subject to fluctuation ) for instance.