Facebook's Killer Feature

At lunch today I had a revelation. If Facebook expanded their privacy settings just a little bit, they could end LinkedIn’s success. Imagine if you were able to control all of your identities from one location. There would be three generic profile settings (or privacy categories): friends, professional and family. For each of those you can control which items users in that category could see.

Additionally, you could select what individuals could see, in the case that the general privacy settings did not fit them accurately. Once that occurred, Facebook would be capable of completely replacing all functionality that LinkedIn provides. What would take this one step further is the ability to control what applications each privacy category could access. I previously discussed this feature set and have thoroughly considered developing it within an application. Rather than investing the time and energy, I think Facebook should release this as an extended feature. Do you think this would be a useful feature?