If I see what you're up to on Facebook but I don't see your updates on Flickr, I'll still care about Facebook.

If you're building a social product, you're still living in the last century if your product doesn't work on Facebook.

Right now, nearly all the apps on Facebook take a week to build. No more.

The very first company I started failed with a great bang. The second one failed a little bit less, but still failed. The third one, you know, proper failed, but it was kind of okay. I recovered quickly. Number four almost didn't fail. It still didn't really feel great, but it did okay. Number five was PayPal.

Media is very different from financial services. People are very fickle and very vocal. They believe that things should be one way and not the other. It's still very rewarding to build products for huge audiences. It feels like you're making an impact.

The single most important top-level trend is the shift to mobile.

You can have successful teams where people hate but deeply respect each other; the opposite (love but not respect among team members) is a recipe for disaster.