Bitcoin allows for any company to implement Proof of Solvency by making public the Bitcoin Address in which they store their customer’s funds and proving that they control the private keys to that address. From that point going forward anyone at anytime anywhere in the world can look up the balance of that Bitcoin address and know whether or not the company has the reserves it claims to or not.
Consumers who are security conscious will likely only choose banks and other companies who hold their funds that allow for public Proof of Solvency. Banks and companies who do not implement this feature will eventually go out of business or implement it.
This means that the practices of Fractional Reserve Banking and Fractional Reserve Lending are no longer feasible in the future.