http://bentasker.i2p/posts/blog/general/695-an-analysis-of-search-terms-used-on-bentasker-co-uk.html
However, it is used relatively rarely - most visitors arrive at my site via a search engine, view whatever article they clicked on, perhaps follow related internal links, but otherwise don't feel the need to do manual searches (analysis in the past showed that use of the search function dropped dramatically when article tags were introduced).