Would stongly advise against using paypal...
Whats wrong with paypal?
I was actually slightly interested but will probably do LTC to BTC
The basic scam is that the buyer disputes the transaction, and they get their money back and they keep the LTC/BTC.
There are some twists to the scenario (such as the buyer paying as a gift), but either way it can end with someone losing their money.
The topic has been discussed a lot. See if you can find threads with more detail.