Google Webmaster posted an SMX Advanced Q&A: “Q. Can I customize the content of a page or redirect the user based on the terms in their search query? Or is that considered cloaking? A. If you're redirecting or returning different content to the user than what Googlebot would see on that URL (e.g., based on the google.com referrer or query string), we consider that cloaking. If the searcher decided to click on the 'vintage jewelry' result, you should show them the page they clicked on even if you think a different page might be better (emphasis added). You can always link between related pages on your website (i.e., link to your 'vintage jewelry' page from your 'vintage cameos' page and vice versa, so that anyone landing on those pages from any source can cross-navigate); but we don't believe you should make that decision for the searcher.”

Full Post: GWC blog