Over on the University of Virginia's admissions blog, Senior Assistant Dean of Admissions Jeannine Lalonde got fed up with the misinformation she was seeing on forums and message boards about how many recommendation letters to submit to a college.  She struck back with this bit of valuable information about how the admissions office uses recommendations:
Your counselor's recommendation will be the one that sets the stage. They usually talk about the "big picture."  The go beyond the information in the school profile to tell us about your class and what big choices you may have made about your academics.  Your teacher's recommendation will be about the day-to-day.  They are often more personal and more anecdotal.  They tell us about those great contributions you've made in class or the projects you've done that have gone beyond their expectations.

And as for whether you should submit more than the requested number of recommendation letters?
No one at UVa wants this.  No one.  Colleges ask for the items they would like to receive. 

Read her full comments on the Notes from Peabody blog.