Nielsen claims in his new article Mental Models For Search Are Getting Firmer that users are getting confused if a Button labeled with the word search is used for parametric search. The reason is, according to Nielsen, that users have precise expectations for the behavior of search.
(…) Although often useful, such searches don’t fit the design pattern for search. You should thus call them something else to avoid confusing users.(…) In our experience, when users see a fat Search button, they’re likely to frantically look for the box where I type my words. The mental model is so strong that the label Search equals keyword searching, not other types of search. (…)
related links
Mental Models For Search Are Getting Firmer
Guidelines for Search Usability