I stumbled upon something an hour or so ago when looking for some vegetables high in iron. When I typed in the query, I was presented with a SERP that I'd never came across before...
This is another example of a search query that is completely owned by Google, i.e. it fulfills the needs of the user without any requirement to visit an external website.
We've started to see a lot more SERPs appearing that encourage a slightly different type of behaviour from searchers. The carousel was a fairly big step in this direction, but even then you would be clicking through to an external site. This increased emphasis on servicing the needs of the searcher in as little clicks as possible could eventually have a huge impact upon some websites.
Considering the level of interactivity within this specific SERP, it allows for a user to gain multiple facets of data across a number of different entities (in this case, vegetables) without even inputting a different query.
As Bill Slawski alluded to me, this is a great example of the work that Google's deep web crawl team are working on (source: http://www.cs.cornell.edu/~lucja/Publications/I03.pdf). I wouldn't be surprised if we see more interactive SERPs like this over the coming weeks/months.
Keep me posted if you see any!