The cynic in me says that facebook is doing this because the employers didn't go through the proper channels (i.e. pay facebook for that kind of access) and it's a message: If you want that kind of data, you have to pay for it.
I hope this isn't the case, but facebook doesn't really have a great record when it comes to privacy.
Your cynicism is somewhat warranted, but slightly misplaced.
Facebook is doing this because not doing so would be really bad for business: i.e., it would threaten the user experience of the site. People would either quit Facebook, spend less time on it, severely tone down or alter their usage of it, or create fake profiles for work. Any or all of those things would be a big detriment to Facebook. So taking a stand on this issue is both good for business and good for PR.
I don't think Facebook would want to sell its data so obviously just offering users' profiles to any business that comes and pays. This would be too bold of a move.
I hope this isn't the case, but facebook doesn't really have a great record when it comes to privacy.