“Our algorithms use a wide range of information to predict the queries users are most likely to want to see. For example, Google Suggest uses data about the overall popularity of various searches to help rank the refinements it offers,” states the Google Suggest FAQ.
That means in the past someone actually searched for “dinosaurs were made up by the cia to discourage time travel.” Wow. Plenty more Google Suggest screenshots to come in the future. This was actually funny enough to get its own dedicated blog post.