If you're not covered by SIPC (FDIC is only for banks) in the event that your securities have been lent, then anyone with a margin account at any broker is at risk. If you have a margin account, in almost every case you've also agreed to allow the broker to lend your shares. In the vast majority of cases you don't even know when "your" shares have been lent and you're not compensated (of course in reality the broker holds all the shares under a street name in a big pool and just lends out of that pool). That means that all of us with margin accounts could have a large number of our stocks that have been lent, and not even know it. Signing up for the yield enhancement program doesn't change that at all, you'd be at the same risk simply because you have a margin account.I *THINK* and I can be wrong here:
You are 100% FDIC/SIPC covered for stock positions up to 500k.
I *THINK* you are NOT covered for the positions that are LENT OUT.
Note: There should be little concern about a company like IB going bust and loosing the ability to reclaim your lent out stocks. But still risk... ergo, I wonder why one would do this.
That said, from my research the real risk is if the firm your stocks were lent to went under, i.e. if IB lent stock to PFGBest, when PFGBest went bankrupt IB became an unsecured creditor in the back to of the line to receive those securities back, behind all of PFGBest's actual customers. In most cases IB would just eat that loss and you as a customer wouldn't even know about it. In fact they make so much off the cash cow of lending fees that they can afford to have a counterparty go bust every year or so and still break even, but I suppose if it happens to someone big enough with enough shorts it could have a domino effect.