This is actually a lot more interesting than I first thought. It IS really anonymous since my IP is never exposed to anoyone else than the friends I add. If I add a friend, Kalle and Kalle adds a friend, Totte then Totte will never see my IP adress and will never know if he is downloading a file from me or Kalle  (or some other friends friend for that matter). This way you truly do have a circle of trust where you are protected. Pretty darn smart.