I honestly don't know now that I'm rethinking of it. It's an interesting experiment, I ought to say. One thing I'm sure I'd do is search for the owner, and not at the beach, because most (or some) would say it's theirs. If they knew it's cash, most would definitely rise their hands.

If I could somehow know that there's only one paper wallet with this private key, and the true owner has no other way of accessing these funds, I'd take them for the same reason I'd take cash found on the street. However, taking bitcoins appear to raise moral issues, because ownership can be distributed in several places.

What I yet don't understand is: What grants you ownership rights, if not the private key? Car ownership is granted by the law, and same is true for almost every asset. For that reason, I'm not convinced that taking the keys of a car is a good analogy to taking the private key of a bitcoin wallet, and no one should be. It might be a good comparison morally-wise, but not beyond that.