Ashley is trying to sell his MacBook Air on Craigslist, and the person most interested wants to pay through PayPal and have it shipped. Leo says that the benefit of PayPal is that there are guarantees for payment. However, there are cases when those guarantees are not enough. So it's important to take a close look at what PayPal will do to protect him. He should look at their buyer ratings on eBay, if they have them.
It's always hard to prove if they got the item, and they can always say they didn't receive it. So he should make sure he is protected.
From the chatroom - offering to pay more than what he's asking is a common scam to get him to overcome any hesitance.