H i all, Sam Shrauger here. I was interested to see David Sacks' Quora post republished on Inside Facebook  yesterday in response to the question: Can Facebook Credits replace PayPal one day, why or why not?   I think David raised some fantastic points about the relative costs of PayPal and Facebook Credits, as well as the value propositions both the PayPal and Facebook Credits systems provide to users.  More than anything, however,