Yes I've read that FAQ. But please read my question carefully: I'm asking what are the effects of BB, not what affects BB.
Mostly each point of BB hurts your vassal's loyalty. It's the "reputation" loyalty hit mentioned in the tooltip. If you have a small realm and high intrigue this isn't a huge problem -- most of the country is your desmene so you don't need no stinking vassals. If you're Germany BB really, really, really sucks.
It also affects diplomacy greatly. Other countries are less likely to agree with a treacherous bastard. In practical terms CK diplomacy is limited to diplo-vassalization, marriages, and revoking titles. Diplo-vassalization is always a long shot, but it's totally useless if your reputation is tarnished. BB doesn't seem to hurt marriage prospects much. I can't tell you anything about revoking titles. I never try.
Note that Counts and Dukes pledge allegiance to their natural liege voluntarily if he's got a good reputation. So if you want to re-unite a fractured Kingdom the best thing to do is get rid of BB. Eventually everyone will come back of their own accord.
Nick
