Last weekend, my friends and I coded up a prototype Facebook app that needed to know (1) the gender of your friends and (2) a school or company that they are or were a part of. Using the Graph API, I was only able to get that data for 33% of my friends.
IMHO, that seems rather low given that gender + company / school really isn't something most people care about keeping private (as opposed to, say, photos). My hypothesis is that because of privacy concerns over the recent Facebook changes, a lot more users are either removing or hiding that data from FB apps. However, I'm not really sure how valid that is because (1) my friends are not a representative sample and (2) I wasn't systematically looking for this data prior to FB's changes.
So question for the FB apps developers out there: Have you noticed any drop in the quality or quantity of information you could access post-Graph-API? I'm not trying to formally prove anything here -- just seeing whether or not I'm completely off base.