At university I conducted a report showing the differences between an individual who searches via typing as oppose to speaking. What I found was that when individuals spoke out their desired searches, search phrases tended to be much longer. As a result of the elongated searches, test subjects found that they were receiving more specific results to their needs.
When longer search phrases are put through search engines, the "by chance websites" are filtered out ("by chance websites" was a phrase coined during my experiment and means the websites that pop up in a users results page that are not directly relevant to the search phrase but may have been picked up because the search term used was too ambiguous e.g. Car), and more relevant websites are brought to the front page.
In the world of seo, websites tend to use short phrases as their keywords and in their adwords and the websites that were returned to the results page had in depth content and more often then not, small websites were trumping larger ones.
To conclude, the seo strategy has changed when using adwords, longer phrases should be used to promote your site, and although longer phrases will not drive a lot of traffic, they will ensure that it will not be a wasted click. However, websites must ensure their content is up to date and written for humans.