There is an interesting discussion going on at Digital Point about WebmasterWorld’s cloaking setup. Basically if you click on a result in Google for WebmasterWorld, you get sent to a login page, where they suggest you pay for a membership and very small type where you can login for free. So basically the average user gets a login screen and the googlebot gets the actual page content.
There has been a bunch of talk about this, but I have yet to see anyone from Google say it is ok. Of course WMW is fairly well known so you’d think if there was a problem it would have been noticed by now. If this is ok, it is a great way for people to get more subscribers to their website–show the results in Google, but don’t let them see it until they sign up.