@evan my previous answer was flippant…

The question seems to ask whether we have some moral obligation to inform people, to which I think the answer is obviously not. If somebody I’m not expecting knocks on my door, I have no obligation to open it or even to be at home. The knocking can just be un-acked.

But… I still voted “no, but”. I definitely think you can tell them, and it might even be a kind thing to do, depending on the previous relationship you’ve had. I would feel pretty bad if I was close with somebody, or they depended on me, and then I locked them out of my life without a word.