Letters of exclusivity are an annoyance that I only think about when I receive one. Does anyone find the requirement to sign exclusivity agreements on bids anti-competitive and hardly something that should be required by donors who insist on promotion of market principles in their economic development interventions?
In the private sector, these agreements are called options. If a firm wants someone and wishes to exclude other firms then they should pay for the privilege. The fact that the donor - USAID for example - instructs bidders to obtain exclusivity letters (of dubious enforceability, but that is another matter)is at odds with its mission.
Consultants required to sign these agreements should be paid for their exclusivity. If the firm wins the bid, the agreement can state that the exclusivity fee will be applied to the compensation and the firm has lost nothing. If the firm does not win, well welcome to the market. Otherwise, consultants should be free to attach their names to multiple bids.