If you want to build a service which is not just serving rich people, then you need to have something that people can afford. ... At Facebook, we are… - Mark Zuckerberg

It is better to buy than compete. (from a 2008 email)

I think that some decisions that we made early on to localize the website and keep it separate for each college on the network kept it really useful, because people could only see people from their local college and friends outside. That made it so people were comfortable sharing information that they probably wouldn't otherwise, which made it useful in the long term for people to look up information about other people on the site.

Understanding who you serve is always a very important problem, and it only gets harder the more people that you serve. We try to pay a lot of attention to this by a combination of very rigorous quantitative and qualitative feedback. But if you’re serving 1.2 billion people, it’s very hard.