Eric Bramlett, a local seo expert, discoverd that Trulia, a popular real estate search site, has been cloaking their partner pages. This is clearly against Google’s TOS and there is a good chance they will get penalized by Google. Well after eading his post, I did a little more snooping my self and found they were cloaking the of the following pages as well:
Update: Trulia has taken down their cloaks. It’s amazing what a little peer pressure will do.