Today SEO Blackhat actually showed yet another threat to the traffic you get from your top rankings Google answering queries that are in the form of questions in Google suggest meaning for those of us that get "what is XYZ" queries driving traffic might see less traffic coming from those terms.
Being a good SEO I had to try this myself this time I used the question "what is a short sale" which showed the following:
Looking at the description source it is coming from a Princeton University language project. If you actually click on the result it doesn't take you to that site, instead it takes you to to a Google page that has over 14 definitions.
Here's a shot:
I would imagine that the sites Google pulls in are for the most part "quality sites" that have passed some kind of algorithmic sniff test. This lends value to creating glossaries for even the most niche content. Not only are there HIGH Quality sites to submit glossaries to but they are also starting to show up all over Google properties. Take the example below of buying guides showing up in Google Product Search.
Implications in E-commerce SEO
E-commerce SEO's check this out, we all know all about Google adding images into paid search (as shown below), but have you seen the buying guides that Google is showing in product search (scroll to the bottom).
Or see for yourself:
Take notice to the "view more buying guides link" on this page when clicked it showed a pretty average looking review page that fell into the "more results" (see thumb below) instead of the top 3. Google is definitely seeming to in this example reward sites with good images (buying guides with images likely attract more links, versus snowboard buying guides like this, over time I'll be doing more research on this to see how links and other things could be impacting rankings.
Either way guys and girls, at the end of the day, creating guides, glossaries, etc (yes, just good useful content) seems to be a content development strategy that Google is rewarding, so get on your horse. Don't allow yourself to be lazy and say "theres already several how to buying guides or glossaries in my space", which is likely true, just get more deep, hit a niche of a niche, but start writing. Your rankings & traffic may depend on it.