Well, if you make it clear that you have a pinglist, then when you post a thread pertaining to it, people can ask to be on your ping list if they find it interesting. And you should probably say in your comments something like "send me a private message to subscribe to this pinglist". You can look at PJ-Comix's DUmmies threads to see examples.
There was this one troll though, I guess about a year ago, who basically just put people onto his ping list without their permission, and pinged them to threads with articles about US casualities. He lasted about maybe a month before getting banned. Interesting, this guy, or someone with the same MO, made a reappearance this year under the screenname SGTNYC (banned also).
But I digress. Basically, I think it's a no-no to just add someone to a pinglist without them asking to be on it.
I guess what I am asking is where do you keep the names on your ping list, so they are easily pinged.
My Pingees are all legit.
I will VERY rarely add someone who hasn't asked to the Kitty Ping List, but only with rock-solid evidence that they are interested; e.g. a handle like ILUVCATZ. Only added one or two this way.
The Kitty Ping List started by accident. I suddenly acquired Zia, my first (and to date only) kitten, and in a panic I posted a vanity thread asking what to do. (Typical Response: Feed it to your dog. :-) )
People then started asking me to ping them with updates on Zia, so I did so. Then people started asking me to add them to my kitty ping list. I hadn't realized up to then that I had a kitty ping list, but now I certainly do. In short, I acquired the Kitty Ping List in much the same manner I acquired my kitty.
At last count, the Kitty Ping List had 61 people. Plenty of room for more.