Google tends to get flack from webmasters about the usage of snippets in their answer boxes.  Bing is definitely taking this a step further by putting the contents of entire Wikipedia sections and pages right on their Bing search result pages.

Here is a Bing search for SEO, and the resulting answer box in animated form, showing as you scroll through the individual tabs.

Here is another example in non-animated form for another search query.

And here are what some of the tabs look like when you click on them. Searchers can side scroll to access additional sections from the wikipedia page, and it expands for longer content.

And another few examples of the Wikipedia answer boxes.

They also include “Text under CC-BY-SA license” with the link going to this Creative Commons page.

This is similar in style to the recent recipes and drinks that Bing added to their search results, with tabbed options for going between tabs for further content.  However, in the cases with recipes and drinks, it appeared to be a partnership between Bing and the websites featured.

Some of the tabs are truncated, while others expand downwards to show the entire content from that section of the Wikipedia pages.  But it is a huge amount of content that Bing is displaying in their search results pages from Wikipedia.

This seems to be a test, as I did a search for the same query in another browser, and got the usual results without the tabbed Wikipedia content in the search results.

This is quite an interesting change for Bing to include this.  The fact that they are including the link to Creative Commons does hint that they considered whether people would consider this too much content from a site to be displaying in the search results as an answer box.