If you don't want people to know that you're friends with Dave, don't friend Dave, or don't use it at all. This isn't supposed to replace pseudo-anonymous networks like Twitter, this is more like Facebook without all the bullshit. The use case is "I know Dave, and I don't care who knows that I'm friends with Dave, and I'd like to let him know I won't make it to the PTA meeting without involving an enormous advertising corporation".