PayPal is pretty safe man, cause the account is directly connected to the person's credit card or checking account, so if they try to pull a fast one, PayPal will freeze that person's account and put a hold on the account for the amount that you paid, so you'll get your $ back instantly if they do.
But I wouldn't trip, he met the dude in San Carlos or Palo Alto or some shit, the dude will meet you halfway. So its not that bad.