Bing seems to have recently made some changes to its Quick Previews box, inserting reviews from Amazon.com and answers from Yahoo Answers when users mouseover the arrow to the right of the search result to get more information about a website. It's not clear yet if this is a test or a permanent change.
If you search for a product or movie on Bing, for example, now if Amazon.com is one of your search results, you can read a product review without ever visiting Amazon.com. Here's a screenshot via Microsoft News, which first reported the change:
Yahoo Answers have also been integrated in Bing's Quick Previews. If Yahoo Answers appears in your search results related to your query, Bing will show you the full question in the preview box. Here's a screenshot, also from Microsoft News:
When Bing launched Quick Previews (for those unfamilar with the features, it pre-dated Google's Instant Previews, but is a much simpler text-based preview than Google's offering), users were simply shown more information about the site by hovering over the arrow. Now, users can also find links to popular links/sections on the website, address info, contact information, and more.