It's just cool to see what kinds of things people have been searching for that brought them here. It also gives a feel for what the search engines think your site is about.
I can see privacy issues being raised by people who don't particularly want their search queries immortalised on every search result they visit, which is why members will easily be able to configure how many hits to display, or not to display them at all. Loging into the main site will give complete detailed stats anyway. Besides, the queries are completely anonymous. Fun for the whole family!