Those are great points, but I do wonder how many people who use Facebook are really that careful about cleaning up their profile or thinking through what their choices are saying. Many people don't even realize how personalize search engine results are. Even though facebook results will obviously be personalized, I doubt most people will really think through the consequences of these bubbles. As you said, it's hard to stop them when everything you do affects them.
My hope is that in the long run, search engines and Facebook both start showing broader, newer content to people, perhaps to test advertising potential, and balance out the narrow space we're driving ourselves in to.
We'll have to keep watching and learning!