Thanks for the feedback. I just wanted to correct you on one point:

mixes have two settings: visible_to and editable_by. Only mixes that are editable by everyone fall into the category you describe. People can choose "self", "friends" or "everyone" for any mix.

I think the problem is not the privacy, it's the complexity and lack of a good user flow... what was your experience going through it? Did you give up at a certain point? Was it kind of lame?

I feel like I need to get a web designer and just re-design the experience.