PayPal transactions are irreversible [...]
It's not? Many people scam others by charging back/contesting a transaction. There is literally a pinned thread by theymos on the Currency exchange that is called
Beware of PayPal and other reversible transfer services.
Money sent through PayPal and any other money transfer service that accepts credit cards can be easily reversed by the sender, even after several weeks. Therefore, you should only accept PayPal in trades with people you trust very highly.
This is why newbies are not likely to sell their PayPal USD for bitcoins successfully.
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