Say you do a search for a particular location, the first thing that pops up to the the top of the page is a box with some information pulled from wikipedia and a link/image of it on google maps. Search for a band, and you see the same with links to youtube and google music. Search for online storage and you see the same thing.
While google has been audited time and time again to prove that their search engine totally allows competitors to make an impact against some of these sorts of things. Even without the box, the builder of the worlds most used search engine is certainly very good at search engine optimization for their own products.