Imagine a research database, that upon searching for "wind energy," gives top results about the benefits of turbine technology to one student, while another student (with a different search history, or in a different state) is instead shown articles that focus on the noise and vertigo that wind turbines produce. Sound fishy? Google has unveiled a more personal search that does exactly this sort of thing, called "Search, plus Your World. Is this more about advertising revenue than providing access to information? For a nice review of the issue, see a competitor's Escape your search engine Filter Bubble! When, if ever, would you want filtered results?