Google's Matt Cutts recently did an almost 9 minute video on the topic of cloaking, he called the video the "definitive cloaking video."
Here are the main points:
- Cloaking is showing different content to users than GoogleBot.
- Cloaking Violation of Quality Guidelines
- Cloaking is High Risk
- It Is Often Used For Deceptive Reasons
- No Such Thing Has White Hat Cloaking
Matt then goes through various things to look for when a site might be cloaking.
What about geolocation or mobile devices? The general rule is you "do not need to worry about it", because it is not cloaking. Why? As long as you serve GoogleBot was U.S. users see, then it is not cloaking. Same thing with mobile devices, because you should treat GoogleBot as a desktop user.
He gets into more details in this almost 9 minute video below.
Forum discussion at Google +.