Elinor Mills has a story at cnet about Google's Postini.
http://news.cnet.com/8301-1009_3-10276548-83.html

They provide a pay service for discriminating desirable e-mail from spam.
Craig Croteau discusses the Sentinel test system. Kevin Lund talks about their "Zero-Hour" technology.

"We take (spam) seriously, but we're not on some crusade," Lund said.

Scott Petry, Postini's founder, was also interviewed.

"Estimates now put it as high as 90 percent of all e-mail, with virus-related messages ranging from 15 percent to 50 percent of the total, according to Postini."

I wonder why Google doesn't use Postini's technology to improve Gmail's spam filtering.

The Postini and Gmail teams are starting to integrate both processes. Since Gmail already had very good spam detection, there was likely no immediate need to reconfigure Postini to filter Gmail. And Postini was an enterprise feature to begin with, so business verticals probably played a role as well.

For my standard Gmail acct, I'd have to say spam detection accuracy is >99% accurate. Its been several weeks since a spam email made it to my inbox and I get on average 10-12 spams per day. Its so good, I rarely view the spam folder any more.