This morning, following a friend's status update, I looked at my contacts list on FaceBook, and was horrified to see a huge list of friends and their _phone numbers_! (If you want to see it yourself, you go to Accounts, Edit Friends, and Contacts)
On the page, FaceBook says "Facebook Phonebook displays contacts you have imported from your phone, as well as your Facebook friends. If you would like to remove your mobile contacts from Facebook, you need to disable the feature on your mobile phone and visit this page."
My initial reaction, looking at great swaths of phone numbers that I'd never seen before was "Oh no! FaceBook's done something bad again with privacy" (or words to that effect), followed by "And _I_ never gave permission for my contacts to be imported from my phone!", but after I looked at it for a while, I realized that the list did not have my phone's contact numbers at all. And not only that, but the list did not have all my friends on it.
What I was actually looking at was a list of my friends that had ponied up their own numbers. Perhaps they'd come from some of their phones, but a bunch that I checked were simply what people had put on their own profile, including one memorable one of +10000000000 (R.A....You know who you are).
FaceBook didn't do anything bad, they simply assembled available information, from your friends, in a neat list.
It was just a shock to see it all at once.
Really, the only downside is if your privacy settings are open to the world, and in that situation, it is not yet clear if that might leak your friends' private information.
Perhaps that's a topic for another day.
Keep safe folks.
Roger (Btw, I am currently an independent security guy, _not_ something to do with AVG. Even though they're still my friends, I no longer work there)