I think that this is slightly incorrect, regarding the mechanism by which the collateral protects the lenders of shares.
Yes - Fidelity (or whichever brokerage you're with and has borrowed your shares) will collect that cash collateral from the borrowers of the shares, and yes that cash is deposited with a third party bank (FDIC insured account). The role of that collateral is to protect the share lender/owner (me) in the event of default by the brokerage, with me (the share lender) able to withdraw the full value of the cash account (102-105% of yesterday's closing value) IN LIEU of receiving back my shares.
But for me to be able to take the cash back, Fidelity has to be in default regarding the shares they borrowed from me (default meaning they are unable to perform when my shares need to be returned, for whatever reason). It isn't a convenient option, where Fidelity elects to either return my shares OR elects to return cash in lieu of shares. It's a default event, and the cash collateral means I don't need to wait for the bankruptcy court to decide how much I get back, and what form I get it in.
For obvious reasons, Fidelity is HIGHLY motivated to make sure that never happens. And this is why I'm comfortable having my shares lent out. I also understand why
@TrendTrader007 or anybody else elects to eliminate even this small bit of risk.