Well, maybe it's possible to cancel/add a ping? Perhaps you've pinged the wrong person; or that you forgot to Ping someone. It's pretty useful to cancel/add it.
I understand that canceling a Ping might be a bit difficult..maybe, if someone canceled a Ping, it won't show up in the regular Pinging space. If there is a canceled Ping, if she/he goes into the Forums, it'll say, "You have 'x' Canceled Ping(s). Open Canceled Ping?"
Just a quick idea. :P