Initially I was concerned with the security of PayPal.  Indeed my wife is a CPA, and has attended a few very informative professional development classes where the instructor described various forms of credit card fraud.  While many of these problems may remain for many entities, I have never experienced a problem with PayPal.  I have channeled approximately $100k of funds through PayPal in the past few years, and PayPal has been flawless.  Their security and accounting remains perfect.