It cant be charged back even if you say it was unauthorized. In order for paypal to believe it wasnt you who sent money you would have to get into your paypal from different mashine and send money but in that case you are subject to fraud? People paying from their paypal accounts can't claim personal payments for bitcoin.
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Unfortunately, we are denying your claim because your purchase was for a
virtual, digital, or intangible item, which is not covered under PayPal
Purchase Protection. We only cover claims involving physical items that can
be shipped and tracked.
We encourage you to work directly with your seller to resolve the problem.
You'll find their contact information on the Transaction Details page.
Sincerely,
PayPal
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Scammer is going to tell the truth? It CAN be charged back, happens all the time.
https://bitcointalk.org/index.php?topic=14632.0