I live in an urban area where there are not enough parking spaces for all the apartments, so residents need to use street parking. Street parking space is scarce and coveted. There's a guy on our street who has no fewer than three cars that he keeps parked on the street all the time. He only uses one of them. Every week when the street sweeper is about to come (so street parking is temporarily prohibited), he strategically sits there for two hours, to guarantee that he gets all his spots back.
If ever he does use one of the cars to go somewhere, he backs up one of the others halfway, so that it's now taking up two spots. Then when he gets back he pulls the other one forward again. This way no one can ever take his spots, even when he uses one of the cars.
He seems like quite a nice older gentleman when I talk to him, but I find this behavior pretty egregious. He may have no other option than to get rid of two of his cars, or pay to have them stored. There may be emotional attachment to the cars, and he may not be able to afford to store them.
I don't have any expectation that he'll change his behavior (since he doesn't have to). If what he were doing were illegal I could report him, but I don't think it is. I think part of being honest with my neighbor is telling him that I think what he's doing is wrong: he's wasting a precious public resource. How might I do that in a way that is respectful, and avoids unnecessary conflict, but clearly expresses that I think he is making a moral error?