My users constantly complain that they get too many 'incorrect' results for their query when they make multi-word queries. The problem is that they are used to internet search where the words will be AND-ed together by default. As it stands they get huge numbers of irrelevant matches which makes them start to not trust search. Can you imagine if Google used "OR" for its search queries? Almost every site on the web would be returned for multi-word queries!

e.g. If I search for "andy armstrong pantero" on Google I get 139 results. Switching to OR matching I get 378,000,000 results!!!

Some possibilities here include:
1. Make AND be the default
2. Provide a configuration option so that administrators can choose the default
3. Order search results by relevance so that the AND matches always come ahead of the OR matches

See this idea in the Confluence Community for more details:

http://confluence.atlassian.com/display/DISC/search+exactly?focusedCommentId=169231#comment-169231