you are missing the point of the facebook privacy complaints. it's not that i have any expectation that what i do on fb is secret - it's there on a public website, after all, with multiple people reading and commenting. i do have the expectation that any given conversation i have is mostly noticeable by the people involved in that conversation. having facebook aggregate my activity across the site and make it trivially accessible using my username as the key (and even worse, actively pushing updates to that activity to my friends' streams) violates that expectation violently, and is the main reason i reduced my interaction with facebook to a brief trawl through my friendstream once every day or two.

here's an analogy. suppose i'm at a party, standing in a group of people and having a conversation. this is by no means a private conversation - it is taking place in the middle of a large, open room, and anyone is welcome to come by and participate. i'd still be pretty annoyed if i found out that someone had a hidden microphone broadcasting that conversation to the poolside, despite the fact that anyone sitting by the pool could in theory walk by and listen in any time they wanted to.