Exs, ex hookups, etc.,

So.... Thoughts about keeping in touch with exs ? Keeping exs on Facebook ? 

What about ex hookups ?

This one especially - 

My boyfriend has never even met this girl! They briefly talked on Facebook, he quit "talking" to her because he met me. That was even what he told her. In a way it makes me uncomfortable, that he even talks to her ever. I've brought the subject up before about deleting her, but he says no. Because then she'll message him and be like wtf you deleted me ? My argument is, "you've never even met her ! So you're telling me some girls feelings you've never met are more important then mine ?! " that's how I feel right now. He's more concerned how it'll look if he deletes her, then how I feel. I've never once asked him to stop talking to a female he's friends with. But he's never even met this girl. I feel like it shouldn't even be an issue. 

There are no right or wrong answers! It's just opinions. I want everybody's !! 

I personally don't have an issue if my dude talks to a girl every once in a while that he hooked up with like 5 years ago. I am however, uncomfortable with him talking to chicks he was hooking up with right before him & I started talking.