Google is not just an index and search engine for other people's content.
It also provides a range of services e.g. news, maps, social networking which it preferentially sorts above others. If you were trying to compete in these markets you would be at a disadvantage.
What does it do? Given a music sound input it will give you the exact and song and all metadata related to it.
This kind of apps are the biggest threat to Google. Because they do vertical search far too well. And too many apps like this cut off oxygen bit by bit on the longer run making you vulnerable. Facebook realized this, hence they acquired Instagram.
The thing about Apple and Facebook is they allow such kind of apps to not just thrive but also remain profitable through their platform. I am sure a lot of iPhone apps have eaten into the potential of Google products. Apple's platforms are becoming start up incubators. The same with Facebook. This is the biggest threat. Because they are setting the momentum in a very different direction.
Now imagine, if something like Apple consumer TV brings this platform to every living room. I bet that is going to really hurt Google a lot.
Again, there's an argument there for reinforcing incumbency, but just because something is the second result on a page and so doesn't get the traffic it would if it were first is not equivalent to removing it from the internet (in terms of this topic, at least).
It also provides a range of services e.g. news, maps, social networking which it preferentially sorts above others. If you were trying to compete in these markets you would be at a disadvantage.