The general public should return to sender any package accidentally sent to the wrong address. I think it is unethical for someone to keep something they did not pay for. Especially when the seller sends merchandise to the wrong address, it should be returned. Whomever actually paid for the item and the shipping fees would never receive their merchandise and this would have ill effect on the business that sent the package or the individual whom should have recieved it.
Minimal effort by the receiving member of the public and the mailing company should make this a non-issue. Without opening the package, the person who gets the wrong parcel should find a number printed on the front (the responsibility of the vendor to print it there) and shoule be able to call and request a pre-paid return slip.
I do not believe that the general public should keep something that was delivered to them by accident. A 'finders keepers' attitude is one that isn't fair to any of the parties involved. People should be encouraged to be honest. They should return anything they are delivered by accident. For if they are not, then it causes more issues for all of the parties involved. The original person who ordered it does not receive what they paid for and the company whom it was ordered from loses money from the transaction. It is as though you are being given something to steal and given the choice of whether to return it or not.
I think the individuals receiving parcels misdelivered by USPS have no right to keep the articles, they should simply resend the package back to the postal system, and they will deliver it to the right address. Of course it takes a little effort on the individual's part, but if it was their article that was misdelivered, they would like we do the same.