<p>I know a family friend very well who is an MIT alum. Even though he doesn't know me in an academic setting (just that I'm very motivated and committed), could he send in a letter vouching for my character/personality to the admissions office? I was deferred early.</p>
<p>One or two extra letters won't hurt, and will help if the writer(s) has known you for awhile and can add something about you not otherwise in the application or other letters. My son added a letter from a piano teacher who knew him for nine years. Don't overdo it, though; there's a famous story out there about an applicant who sent in 30-35 additional letters. The adcoms have only so much time to read each application and will likely react negatively to a lot of extra material to review.</p>