I had one committee letter, 5 science, 1 literature prof, ultimate frisbee coach, and my boss for work.
My advisor told me I could have as many as I wanted as long as it fit in the 10-page-maximum-pdf file size or whatever.. that they email directly to the schools. Virtual evals...
I honestly believe that my recs got me interviews. My gpa 3.6 and mcat 33 are below the mdapplicant school averages where i've been accepted and interviewed... Maybe 8 wasn't necessary... but I know the 7 people who wrote them for me very very well so I assume they were consistent in what was said about me. My advisor read the letters for me (I cannot read or know what they wrote since it was confidential) but she told me they were all "great"... so I didn't throw any out.
It's your call though, BUT!!!! go for QUALITY not quantity. I'm just fortunate to have many people to write on my behalf (perks of a small liberal arts school eh?)