The entire concept, really. It's grotesquely invasive, opt in or no, and it speaks to a culture of blatant disregard for privacy as a concept.

On a more minor note I really don't want to know this much about my acquaintances' collective browsing habits.

Now that there's a viable alternative with google+ all I have to do is scrape my photo galleries and that's a wrap.

To me it appears to be nothing more than a redesign of the traditional wall?

Yes, I understand the concerns about the "sharing" of information--something which I think people don't quite understand yet--but other than that I feel like people are up in arms over nothing.

shrug Carry on, then.