I've never really had a brutal break up with any of my exes. So we've all remained friends after.
But eventually your lives just grow apart and you don't communicate anymore. So no, I don't talk to any of my exes anymore. Not because I don't like them, but because I just stopped reaching out to them, and they stopped reaching out to me.
If you're mature, I guess you can be friends with anyone. Whether you've had a relationship or just had a fling.
Time seems to heal most wounds anyway.
I don't understand how people can hate a certain ex (unless they did something truly horrible to you), because at one point, you did care about them, so they can't possibly be all bad.
And if you are wise, you have taken something from that relationship...and learned something about them...and more importantly, yourself.