[neilv]

IME, listing stuff for free gets a lot of people who are cognitively impaired, such as by drugs or some mental illness.

There may also be "choosing beggars", but they seem to be in the minority, and I'm not sure they're distinct from the more general group above.

It also gets flippers (people who grab/buy things to immediately resell them), who are not at all impaired, but some of them are trying to maximize their profit. So if some of them impose, flake, deceive, etc., I get the impression that's all intentional, to make someone else bear their cost of their optimization.

Ways I've found to avoid these people: (1) post to a free-stuff list of a nearby university, where it generally reaches penny-pinching students; (2) post on a public list, like CraigsList, but with an ostensibly nonzero price, then tell the person it's free; (3) put it on the curb with a FREE sign.