Banks should really be scared of bank runs, if everyone took out their money at the same time. It would expose how they run on unsustainable fractional reserves and exorbitant fees. They are "good" at lending out that isn't even there.
Won't banksters just print more of their filthy fiat out of thin air? Ain't that what they do?
With central banks and fiat currencies, yes. Bitcoin has no central bank that can issue more coins, so that particular problem isn't real.
But all commercial or private banks would treat it exactly the same as they treat anything else; they'd have a fractional reserve ratio where they'd loan out (pieces of paper giving borrowers a right to claim) about three times as many coins as the banks actually have. And then charge the borrowers interest, and we're right back to the debt model of money.