jakob nielsen has a very interesting post on mental models for search (through doug cutting). according to him, “users now have precise expectations for the behavior of search. designs that invoke this mental model but work differently are confusing.” jakob focuses on the user interface (search box, button and result list). i completely agree with him, but what seems very important to me is WHAT and HOW the users type in the search box, how they refine their search, aso. the iprospect search engine user behavior study has some quite interesting results, but the most interesting for me was to peek at the user data that aol released (get it here)