How to detect a page request from Safari 4's Top Sites feature
sunpig.com
sunpig.com
No, they won't. Google's definition of cloaking is serving different results to Googlebot versus end-users.
For one thing, neither nor GoogleBot nor the remote quality raters will be sending Safari-specific headers for discovery/evaluation tasks, so they won't see the preview at all. For another, this falls into the (sort of) nebulous category of "cloaking designed to enhance the user experience", which is almost always kosher.
Similar examples: you can auto-detect someone's region/language/browser/etc and customize the page to fit their needs, and Google is pretty much OK with that as long as you treat Googlebot the same way.
I can't remember the name of this, though, so I'm having trouble searching for it. Maybe 2006 or 2007 was the time?