In 2005, I wrote an article that talked about the possibility of Google creating a set-top box, and how it could change the game in a lot of ways. The same is true today -- set-top boxes, for the most part, are really crappy and have a ton of room for improvement.
It sounds like Google is testing running an experiment with the Dish Network -- they are testing a box, powered by Android, that makes it easy to search for shows and integrates web video content with live television content. Not only will Google technology make watching and finding content easier, it also puts Google in a great position to make their TV ads offering more valuable.
With strong partnerships with cable and satellite operators, Google could eventually make buying television ads as affordable, and contextual as web ads. Imagine logging into your Google account on your set-top box, and having relevant television commercials displayed during commercial break. It's possible, and maybe even probable if you fast forward 3 to 5 years.