If you’ve used Google Suggest or the Firefox built-in search, both of them suggest common searches as you type. For example, if you type “Britney”, it might suggest
Britney Spears Shaved Head
…and so on. I know Google can do this because they have a huge database of what people have searched for before. How Firefox does it, I don’t know (unless they record searches and built their own list).
Without building your own list of searches, which would take a long time to get to critical mass, how could one do this? If there were a web service or API or database of common searches available, that’d do it. But so far I’ve been unable to locate any approach that would be quite comprehensive.