I think it is allowed now... read this - https://www.thepaypalblog.com/2010/...to-pay-for-facebook-ads-and-facebook-credits/
I see, but I don't get that option; the "Add PayPal as funding source"! Is there a list of Countries that are entitled to the facebook/PayPal payment?
Finally got some answers... Now Facebook users can purchase Facebook Credits with PayPal, and can use those credits for virtual good purchases with all applications that accept them as part of our beta test. This new option is live in a few applications to a small percentage of users, and will roll out more broadly over the coming weeks. If PayPal is not yet available for you, please be patience at this time. You can still use the following payment methods to purchase Facebook Credits... So much for adding a little Buy button, their staff must be underpaid...