Naive? How about you not be so technically boring.
Comments API Facebook doesnt need to pay anyone for traffic. That's the truth of the matter. This site wanted an easier system to administrate.
Black helicopters aside, it solves an array of technical issues webmasters have to deal with.
I agree some sites want to stifle dissent. Im just telling you how your argument about making money... totally untrue and doesn't make a lick of sense from FBs side.