Let's suppose you are 28 years old and have completed a graduate degree. You are going for an interview for the job you've always wanted. All your youthful indiscretions have passed into distant memory. You put on your new suit, tie your tie, and head into the future.
You expect to see a friendly face at the interview because you had a 3.7 as an undergraduate and did well in graduate school. But that face isn't so friendly, he's looking at you askance trying to decide whether you're the person on the resume or the pictures of you drunk as a skunk, in various versions of undress, on the new Facebook timeline?
America always has been the home of the second start. You could remake yourself into what you wanted to be by hard work and by changing your attitudes on life. That's going to be hard to do now since Facebook permanently has the picture of you and your then girlfriend on your site. This new feature should make a lot of people run from Facebook. The current generation's belief that everything should be open and available on the web will be tested now.
Facebook has already been selling your information to those sites who sell your life story people find near their Google mentions. One of the things a person in HR does is to protect the company from hiring loose cannons. In a job market which is very difficult, why would they hire you?