For me Sexual History = Ex (1 way or another)

For me I would treat each relationship differently due to the intent which both your girlfriend and their ex have. Then again I would treat it the same as any relationship that my girlfriend had with a guy.

I think we've talked about intention in the past and I look at the intention they both have. If i felt that intention was inappropriate for that relationship and our relationship I would tell her or the chap (as it's better face to face) something to the effect
"look you obviously have deeper set feelings/intentions from your past, you either need to change your behaviour in x, y & z way as I am not prepared to accept this"

Should she be reasonable she should change or tell him to change.

As for me, I act in the way I would expect my ex to act, not to spend too much time with them, talking about them, try not to overdo the touchy feely business and treat them like I would any other friend.

As for FBs, they can do what they like as long as I don't know...