Most go for the "try and buy" model, distributing their games through portals, such as RealArcade and Big Fish, or sites affiliated with AOL, Yahoo!

FORBES: Magazine Article

Facebook primarily makes money through online advertising, both display and search advertising, in which it competes with Google, Yahoo, Microsoft and AOL. However, it has started to tap other business lines as well, like distribution of virtual goods in games and applications.

FORBES: Time Warner Finds A Way To Work Facebook