From our forums'
FAQ, though I admit I had to do a search to find it, since we recently upgraded the forum software around here:
What is the buddy list for?
Some of the features we have enabled here by default, like showing who's currently logged in, lessen the "need" for buddy lists perhaps, but we keep the feature enabled anyway. It can be useful if you need to private message (PM) your buddy list about weekend plans, trip reports or whatnot.