Over at the Google Webmaster Central blog, Maile Ohye is giving insight into IP Delivery, Geolocation and Cloaking.
IP Delivery is serving up targeted content to users based on their IP address. This is ok as long as you treat Googlebot the same as you would a user with a similar IP address.
Geolocation is serving up content based on a user's cookie data, login info or IP address. Ohye says, "The key is to treat Googlebot as you would a typical user from a similar location, IP range, etc. (i.e. don't treat Googlebot as if it came from its own separate country—that's cloaking)."
Cloaking is not ok because it shows humans and the Googlebot different content. Ohye explains, "If the file that Googlebot sees is not identical to the file that a typical user sees, then you're in a high-risk category. A program such as md5sum or diff can compute a hash to verify that two different files are identical."
To sum, treat Googlebot the same way you would your human visitors!
Ohye also discussed Google News' first click free policy. Basically, news sites with premium content can have those paid pages indexed by Google News if they allow visitors to view their first click on the page free. But any clicks deeper into the site are permitted to display a login or payment request first.