Social butterflies know less than they think about their friends’ ethics:
[Researchers] asked groups of workers and business students about ethical dilemmas … [seeking] evidence of "false consensus bias" — that is, the tendency of people to project their values and behaviors onto others. As the size of [individual social] networks grew, so did the extent at which individuals overestimated how many others would agree with them. Why? People discuss "safe subjects in the workplace — sports, kids, current events," the researchers wrote. So "little of the insights that people gain from social ties may apply" to moral dilemmas.
FriendSense is a project out of Yahoo Research designed to answer questions like that, about how much people know about about their friends' values.
FriendSense blurb
FriendSense Facebook application