As human beings we are heavily influenced by what other people use, and depending on who those people are, the more likely we will be influenced by them.

So how does this relate to search? Well, so far, Google and Microsoft have based their searches on things, instead of people. If you searched for recipes for tomato soup, they would find the ones that were most popular by other sites, or their relation to the specific search query. And we get a pretty good result, but from generalized perspective.

Twitter on the other hand is really good at people, or to be more precise, it could be good at it (it isn't really yet). But, Twitter covers what people close to you, in terms of influence, are talking about, and if you can combine that with Google's general results then you have something really spectacular.