No way at all? FB has a lot of servers and a lot of users. They have opportunities for quality practices that few other organizations get.

Here's a simple example:

Split the user population into 365* groups. Assign them to days of the year. Test new code only the group whose day has come up. Follow them until they stop having problems. Now you can deploy that to a month's worth of groups. All good? Deploy to everyone.

Yes, that means that you can't have more than 365 changes in simultaneous development. Tough.

*Yes, yes, leap years. Take a day off from deploying.