indyank - 9:25 am on Nov 10, 2010 (gmt 0)
It looks like webmasters can block these previews by using nosnippet meta tag which which was originally intended to block snippet or description appearing in search results.
Both Google and bing are evil as they seem to say that if you want to opt out of previews, use the nosnippet meta tag, but we aren't going to give you a separate meta tag to control the previews!
While the text in the snippets and the callouts on the previews aren't going to be the same, why do they want us to use a single meta tag to control the different behaviors?
reference - [searchengineland.com...]