WordPress developers will be familiar with many of the problems described here.

I’ve been thinking about this quite a bit lately — writing open source software (where you have a whole variety of environments to support) will be entirely different from working at a company like Facebook (where you probably know more specifically what the servers will look like). Each is going to have his own challenges to think about. Once you get used to developing with certain challenges in mind, it’s probably not obvious what new challenges there will be in a different context.