i have had my fair shares of problems with paypal. It seems they have a bad security problem over there and are in no rush to fix it. They have very little liabilty to deal with and actual make money if someone uses a fraudulent account to buy digital products (they charge a $10 fine per fraudulent sale).

Just be careful, I still like paypal for its ease of use, but have had to drastically step up security on our site rather than relying on paypal's security.