Essentiall PayPal associate FA with bestiality and child porn. Even if it's not the case, they would prefer to shut your account down as opposed to taking any risks.
I would suggest you drop a note if you really intend on grabbing a slot as there is already a waiting list forming for the next round XD It just might start full right out the gate.
http://www.furaffinity.net/view/6903907/