I can't speak from the dominant side, but I can do so from the submissive side.

I would definitely have a problem with a dominant telling me who I could or could not associate with regardless of my past relationship with them. I would hope that my dominant would have enough trust in me to know that I would keep my relationship with them on a strictly platonic level. I would also hope that he would also be secure enough as well.

Personally, I think it is very wrong to forbid anyone contact with another person because we need other people to socialize with, to talk to, and just plain old have around other than our present partners. Granted, I am not really friends with any of my past boyfriends but that is because all of them ended badly.

If my dominant asked me, not ordered me, not to see someone, and gave me a dmaned good reason for it, then I would consider it. But I would rebel at being ordered...or forbidden as it has been put... to see them.