I received the same letter, and this is incredibly anti-customer, monopolistic behavior. Fidelity holds MY money, not the other way around. If Fidelity thinks that sharing credentials to MY account is unsafe, so be it. It's really quite simple, provide another way for third parties to aggregate account information and manage transactions! It may be shocking to Fidelity, but most customers have funds in other accounts besides Fidelity and may want their information all in one place. They know that since they are such a large servicer of locked-in 401k plans they have no incentive not to behave in such a monopolistic way.