"First of all it's not grand theft because he didn't take the MP, it showed up on his doorstep."
You are as clueless as the OP. He signed for it "knowing full well he didn't pay for it" and took possession of it, "knowing full well he didn't pay for it." Grand Theft, period. End of story.
There is no grey area, this it theft, period. Grand Theft to it's true definition; "Taking possession of property valued in excess of $500 federally, $400 in many states."
It is NOT theft, however, if whoever's doorstep it DID show up up, DIDN'T take possession, refused deliver, or TOOK possession and returned to owner or sender. In fact, Mail and Wire Fraud can be even more exciting in Federal Court! I doubt this falls under fraud, but the OP is obviously WELL aware he didn't pay for it, the sender made a mistake, and he/she is
considering keeping it (in which case, it would be theft).
Now, if the OP takes the appropriate steps to return it OR correct the mistake (should NOT be up to the OP to return the package anywhere physically, it should be picked up if re-claimed)...and these steps are documented, he/she can protect the asset and his or her decision.
HOWEVER, and my ONLY point to my previous post....other than my opinion, if he/she is or is planning to keep it (on the sly), it is ridiculous to boast the reception online, period. Whether or not others are envious is another story entirely...religious? Irrelevant. The law is the law (this is NOT an unsolicited goods, doesn't qualify....think BMG tapes and records, book and calendar clubs...that your credit card is incessantly charged for, etc.) and it will ALWAYS catch up with the Dumb Criminals! Guaranteed
J