Google’s ability to mine data from millions of connections, and then leverage that information across its various properties, is invaluable.
It’s why their spam protection is best, it’s why their web security is relatively strong, it’s why they’re overall just good at learning from their data.
They have the Borg approach: get hit with something once, spread the defense to all collective systems near instantly so that it never happens again.
This can be seen in email malware defense like this article talks about, and in the way they do code testing. Before code goes to the Internet it gets blasted with all the existing threats they’ve ever seen–up to and including yesterday–to make sure it doesn’t have any flaws they’ve already been stung by.
They’re just really good at harvesting lessons-learned from their data in near realtime, and that is a security meta-feature that I think puts things like Google Apps ahead of most offerings security-wise.