Stumbled across something interesting today - found that Google is now including a search box in the SiteLinks for sites that use Google search for their internal search engine. The example I came across was w3schools.com - check out the screenshot:

That’s pretty crazy - for smaller sites, that’s a really good reason to use Google search for your engine. When the big G starts including a search box for other sites (hello retail) - that’s going to change the game a bit..

Here’s the link to the search results page.