I had a project recently where the director was lifelong friends with a break_out star, who had committed to doing the film. The agency was non_committal. Why? Because the agency didn't want to tie_up a month of the actor's time for a measly million bucks, when they could be getting 5┦x that from a studio for the same time slot. At the end of the day, a lot of money and time was spent pre_selling territories and shoring up the financing, only to have the star drop out, under target CAA's ('er I mean a random agency's) pressure.
A well written letter of intent for employment can make or break the process of getting an interview. Your letter and resume are supposed to entice potential employers to want to get to know more about you. Make the right impression with a flawless letter of intent and you will be one of those who make it to the next step, the job interview.