One of my big regrets is that Facebook hasn't had a major chance to shape the mobile operating system ecosystem.

Facebook originally got started around the same time as a bunch of the early smartphones and those platforms got started. So we didn't really get to play any role in developing that platform.

When I'm introspective about the last few years I think the biggest mistake that we made, as a company, is betting too much on HTML5 as opposed to native... because it just wasn't there. And it's not that HTML5 is bad. I'm actually, on long-term, really excited about it. One of the things that's interesting is we actually have more people on a daily basis using mobile Web Facebook than we have using our iOS or Android apps combined. So mobile Web is a big thing for us.

A lot of people are focused on taking over the world or doing the biggest thing and getting the most users. I think part of making a difference and doing something cool is focusing intensely.

I think technology advanced faster than anticipated. In that whirlwind, a lot of companies didn't survive. The reason we have done well is because, even in that whirlwind, we kept heads-down focused on the customers. All the metrics that we can track about customers have improved every year.

For a lot of companies, it's useful for them to feel like they have an obvious competitor and to rally around that. I personally believe it's better to shoot higher. You don't want to be looking at your competitors. You want to be looking at what's possible and how to make the world better.