Just to illustrate further why guys, in my opinion, should not keep in contact with even ex-plates. Listen, guys, energy is a real thing. Every person you meet has an aura of energy in them and they give that out to anyone near them. Why I am saying this?
I dated, for about a month, a virgin girl, 23 years old. After noticing that she had no attraction whatsoever to me physically, I ended things and we stopped seeing each other. However, since she works as a receptionist at my cousin's hotel and I sometimes go meet my cousin, I meet her as well since we're not in unfriendly terms overall. Here is the thing: I met her today afternoon and since she was jobless for about half an hour and I had some time to kill after a tiresome day of work, we talked for a couple of things and amidst something I was telling her, she goes "I think I've seen your ex with another guy, holding hands".
First of all, there was no need for her to say that. However, I think she's bitter towards me because I stopped dating her and didn't become desperate or clingy, so I think she kinda tried to "get back at me" and hurt me by telling me about my ex. I had a momentary rush of ego agression since this is the first time someone tells me about my ex and some other, but it is OK overall, it bothers me just a bit and I am aware anyways I am not completely over my ex yet.
What I wanna say with this is that I think we should carefully choose the people we spend our time with and I believe ex-es or even ex-plates are people who either don't want you in their life anymore or that you left and don't want. One way or another, a lot of these people become bitter towards you and believe it or not, will try to hurt you anyway they can, especially if their life is not so exciting (is the case with the girl above). Stay away from people who belong to your past. Nothing beyond a quick salutation and the random chit chat "How's it goin'? Goin' well overall". In ways you cannot imagine, they will try and infect you with their negative energy and will do so especially if they are bitter towards you.
Meet new people, leave ex-es of any kind to the past world.