More than four million businesses have Pages on Facebook that they use to have a dialogue with their customers.

Facebook is inherently viral. There are lots of sites that include a contact importer, and for lots of them it doesn't really make sense. For Facebook it fits so well. It wasn't until a few years in that we started building some tools that made it easier to import friends to the site. That was a huge thing that spiked growth.

When we were a smaller company, Facebook login was widely adopted, and the growth rate for it has been quite quick. But in order to get to the next level and become more ubiquitous, it needs to be trusted even more.

Focus on cost improvement makes it possible for us to afford lower prices, which drives growth. Growth spreads fixed costs across more sales, reducing cost per unit, which makes possible more price reductions. Customers like this, and it's good for shareholders. Please expect us to repeat this loop.

Private brand's important. We invest in quality. We try to treat them like they really are brands, and not just some private label. But, you know, we wouldn't wanna see them continue to grow in percent of total too much. We would like for the brands to offer value to customers and have them grow.

Advertising works most effectively when it's in line with what people are already trying to do. And people are trying to communicate in a certain way on Facebook - they share information with their friends, they learn about what their friends are doing - so there's really a whole new opportunity for a new type of advertising model within that.