Google has open-sourced the updater used by Earth, Chrome, etc.:http://google-opensource.blogspot.com/2009/04/google-update-goes-open-source.html
The blog post above talks about two things: (a) transparency in how Google does things, and (b) saving people time.
I wouldn't underestimate (b), and notably how big a hurdle it is to write the basic "Client Software Infrastructure" today - downloads, builds, upgrade/downgrade, and especially autoupdate. You could spend a few months of a mid-level engineer to do this at a basic level, and a year to do it really right. Some big companies (e.g., Adobe) even make autoupdate clunky and awkward.
Google's system is well engineered, simple for the user, and it works really well.
Of course, Microsoft and Apple should provide these frameworks. Apple doesn't do much here aside from their own apps, though I like Sparkle, which is free.
Microsoft started to provide the basic tools in MSI, though it's not a full framework. But even their lower-level stuff is pretty much broken. A quick list of ways Microsoft dropped the ball with MSI:
1. Their installers are very slow.
2. MSI uses "chained certificates" that usually expire after a year, requiring software authors to chain together all old signing certs to make update work.
3. Uses an ancient compressor, that makes installers that are nearly 2x as big as the better compressors available today.
So anyway, thanks Google. Even though someone else probably should have done this instead, it's a big step forward.