At 8:48 - "These labels are just key/value pairs, and they are really useful for organizing your things. One of the things we learned early on inside of Google is that actually hierarchical representations of things inevitably fall down. You can make up a great representation that's perfectly aligned to your view of the world as a developer, and then the business guy will come along and say 'no that doesn't match up to billing at all. Your view of an application stack doesn't match up at all to the way that we bill for it.' So what we've learned from that is that actually we need to have the ability to have many different kinds of dynamic sets and allow people to slice and query across the state of running things to provide the perspective that makes the most sense for them."