I don't see the harm in it, although I wouldn't argue if someone thought it was inappropriate. I have done it, but not every time.

It's a trash can . . . I personally don't care what goes into mine, as long as it's not illegal, preventing me from putting my own garbage in, or flammable (or something else seriously dangerous).

I'm curious to hear explanations as to why it would be an issue . . . besides the "It's mine, no one else can use it" . . . or "Because it's just gross haha".