> Most companies will eat the cost of shipping mistakes but that doesn't mean you're legally allowed to keep items mistakenly shipped to you.

Yes, it does.

See, back in the day, there was a pretty slick scam going on; scammers would mail out a quantity of cheap office supplies to various places-of-business. The people who received the shipments, used to receiving such shipments, would think it merely a paperwork SNAFU that it didn't have proper documentation or a person to sign for it, shrug, and put it in inventory, where it would be used. A little while later - long enough for the stuff to have been used, or partially - the scammers would send them an invoice for the goods, at ridiculous prices. I mean bottom-barrel office paper, but being billed as if it was the triple-luxury stuff that J.P. Morgan's lawyers would print the final formal version of a major, multi-hundred-million-dollar contract on. The companies would be skewered, because they had accepted delivery and had used the stuff.

FTC put a hard stop to that nonsense by ruling that anything which arrives unsolicited is a gift, and the shipper cannot hold the receiver accountable in any manner.