Before my internship with Google, I wasn't a big fan of unit tests, logging and cloud computing. Now I can say there's a degree of doubt in me when I see some new code without tests and that this code claims to do the right thing.
When you're running code in parallel on 1000's of machines in the cloud, machines whose physical location you don't know and machines you don't have shell access to, your idea of project development changes dramatically. Things like logging and unit testing become your friends.
A good blog on this topic is found on Matt Welsh's blog