There is a promotion campaign going on to get people to verify their payment methods (aka Facebook wants your credit card details and it wants to store them too). So if you haven’t verified your PayPal account or Credit Card on Facebook yet you now will get 30 Facebook Credits for FREE if you do so. Just click here (it is a FB link with the Bubble Witch Saga App ID included) to check if you can use this offer. If you qualify, just go on and fill in the required information. Verifying a PayPal account without a credit card is a bit tricky if I remember right, but doable. Is it worth it? Well… You need to decide what your time is worth. :)
Remember that you probably always want to remove any stored payment methods, READ THIS ARTICLE on WHY and HOW to remove saved payments methods at Facebook.