Facebook's revenue stream, she says, is built more around the networking nature of the application, things like the recent ad design contest on Facebook for the Mazda 3. In spite of the monetizing of click-ads that now appear on each page, Sandberg holds that Facebook's objective is not to compete with direct-response advertisers like Google (where she worked for six years prior to taking the COO position), but on viral and brand ads.
See the interview here.