(So do Oracle, Apple, Microsoft and even AT&T by the way. Cynics here need to remember that.)
One very non-evil thing Google does is let these people loose in their spare time to create and maintain their own projects.
People like Niels Provos (right). Niels, a native of Germany (like my great-grandfather), lists his job as principal software engineer.
He joined Google in 2003 from the University of Michigan and still uses a "Meesh-i-gun" e-mail address. (Go Wolverines.)
Provos just got a little publicity for his Honeyd project, an open source (GNU licensed) honeypot last updated in 2007. Security bloggers promptly passed the story around, in case others didn't know they had an open source alternative.
Honeyd gives small companies the chance to get the same level of security big companies do, by maintaining an old PC on their network to attract and capture malware for further study. Its main competitors, KFSensor and HoneyPoint, are commercial products.
If you're unclear about the value a honeypot will provide you, or just want to learn how one works from the inside you can download Honeyd and put it through its paces. Your only investment is time. If you turn out to have a fraction of Provos' security programming skills I guarantee you will find work.
In addition to security (he's part of Google's security team) Provos has other concerns and interests, both inside and outside the world of programming. He makes swords and is upset over airport security, among other things.
The point is this is a brilliant and hyperactive man. His employers don't hide him under a bushel. They let him loose. This not only benefits Google, which gains a loyal employee, but the community at large.
Which is what open source is really all about. Open source is less about code than people.