This article from Mat Honan at Wired has been showing up in a lot of blogs over the past few days.
If you haven't read it, the story is that the author likes everything on Facebook that he sees. Absolutely everything. As a result, the content of his news feed changes based on the likes.
My News Feed took on an entirely new character in a surprisingly short amount of time. After checking in and liking a bunch of stuff over the course of an hour, there were no human beings in my feed anymore.
I hadn't realised that the Facebook news feed was affected by likes but it should've been obvious had I thought about it. In a way I'm surprised by the size of the effect, but I'm also surprised by the spread of such a non-story. This is a feature article based on a minor observation.
[Update] Forgot to mention that I'm currently running three different browsers. One logged in to Facebook, one logged in to Google, and one for everything else. The ads I was seeing were getting too creepy. Fluid seems to be a pretty good option on a Mac if you want to have separate browsing although you need to pay to get separate cookies.