Actors are paid to act; any agent can tell you that the script is the least important part to them. When it comes to the principal cast (which the sales and financing are predicated), unless I can call the agent or manager directly myself and verify, there is no real attachment. The exception being a Spielberg or a Scorcese whose stature in the industry could reasonably facilitate any star interest.
Some of these instances include: Schools: Many times a school will require a letter of intent when a new club or group is forming. Expansion or downsizing: Letters of intent are sometimes used to let employees of large firms know that the company plans on either expanding or downsizing certain departments.