At the sistersite below, there has been good background information which is not to be repeated here. My interests of a page on PayPal is WebApplicationSecurity concerns and PayPal is said to have a high client satisfaction in that aspect.
It may be of interest to note Paypal ownership was transferred to a company that is linked to XbankSecurityFlaws.
See http://news.com.com/X.com+ceases+banking+operations/2100-1017_3-248389.html