It's not exactly a motto, but it's a phrase frequently heard in Google circles: "Launch early, iterate often."
Google sometimes is chided for releasing most of its products in beta, or during development, and keeping them there for a long time. On the minus side, this makes it seem that Google engineers can't perfect a product; they rely on the users to do that for them. It also serves as a useful excuse if a product is flawed. It's still in beta, after all.
On the plus side, users tend to do a good job at perfecting products, and Google can use the policy to maintain a high level of innovation.
"The idea that you're continually improving the product, that you're continually advancing it, I think is critical to the world of technology, and the kind of consumer technology that Google does," said Paul Buchheit, the lead engineer who developed Gmail for Google before founding his own startup, FriendFeed.
If they just stand still, they're going to very quickly lose their position... but beyond that, there's the risk that as an institution you can forget how to innovate, which can be deadly, because new competitors can come along and you won't be able to catch up with them because you've forgotten how to innovate. It's crucial that a company maintains a continual culture of innovation.