Many people, including myself, observe that Bing produces better search results than Google. But this does not mean that people will switch. Techcrunch has a recent article on this subject. There are various potential reasons behind this unwillingness to switch, such as brand loyalty or the improvement of Bing over Google is not enough.
I wonder if the fact that search is free also plays a role here. In his book Predictably Irrational, Dan Ariely has shown that giving something for free could distort peoples incentives and judgments, making them abandon their usual (more rational) thinking for non-free products. So under the hypothetical situation that people will have to pay to use search engines (either a flat rate or a usage charge or a combination), will this make them more likely to switch to a better product?
Of course, as long as Google stay pat and not charging for the use of its search engine, this may never be an issue. But we never know; Google already started to charge for some of its previously free products.