I just saw this thread over at threadwatch.org about Google's apparent cloaking job, I wouldn't have believed it if I hadn't seen it with my own eyes. Sure enough, they're serving up a different page for "regular" browsers--IE, Mozilla, etc--than they're serving to GoogleBot. And they're basing the page to serve on just user agent, so you can see the so-called cloaked page if you change your user agent to googlebot.
I'm sure we haven't heard the last of this one. Google has some serious explaining to do on this one.