The default privacy settings on Facebook are to let everyone in “My Network and My Friends” see stuff.
This is actually a recipe for disaster, especially for professors.
If you just joined Facebook, then you are looking for people from your past, who are scattered all over the place. And everytime you click on a name, it says you have to be a friend to see the full profile. And so you think that the default settings are pretty private, because you can’t see anything for anyone you look at.
But there’s that My Network thing. Networks are geographically based, and when you join, Facebook encourages you to join your local network. But you aren’t looking for people who live in your city, so you forget about this.
But guess who is in the local Network? All the students at your university, that’s who.