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.
The letter of intent allows for all facts and figures to be verified so that the buyer understands exactly what he or she is getting in the property. If the buyer finds something that he or she can not accept, or something not originally expected, he or she can back out without any recourse or punishment.