I like to pretend all my exes are dead or that they never existed (bad I know)... My fiance is friends with one of his exes, but they never talk and they don't hang out. I tell him everything and he has been open and honest with me from day one. Not all are like that my sisters bf had issues with her talking with any of her ex's, but she has been known to cheat so I don't know if I could think less of them for being jealous.
My personal feelings are that if there are no children involved, why be around each other? If there is a history of unfaithfulness than that would worry me. I usually deny all my ex's access to communicating with me for various reasons like jealousy, doubting their intentions and overall compartmentalization reasons!!
I could have dinner with my ex and his wife would not have a thing to worry about. Unless there is a child involved, I would be friendly but not per say, friends.
All my ex's live in texas. And that is where I want them to stay.