Often, the bans are just because they implemented Federal rules in the most stupid way possible.
For example, the US has something called the "Office of Foreign Assets Control" (OFAC). It's a list of names that companies like PayPal are supposed to prevent from being sent payments.
Paypal chose to implement it with super dumb string matching in ANY field. So, for example, if you put the words "Castro", "Cuba" or "JAMES KANG" into ANY field (even a MEMO field)...your payment gets stopped and your account frozen until you send them the DOB for "Cuba", even though it was just in a memo field.