What difference does it make whether it's a person or not? Either way, it's something you don't need to do anything about now but you might need to do something about in the future.

I treat all waiting-for's as actions. That is, if I'm really not going to do anything about them, I don't have them in my system at all. If I'm going to do something such as remind the person if it isn't done yet after some time, then I put them in my tickle file. When they
come up in the tickle file, they're real actions that can be done immediately or when
I have time, and can be treated like other actions.

I guess the advantage of linking waiting-for's to people is that you can collect all
the things you're waiting for from the same person, along with anything else you
need to talk to that person about, and discuss them all at once when you see
the person.