Citigroup has fallen to $2 per share, a 20% decline on the day and a big drop from the $3.60 it was trading at five days ago. It's spent a lot of this decade around $50. Bank of America is at $3.36. These stocks aren't so much a crapshoot at this point as a single-number roulette bet. If the ball lands on "The government corruptly saves Citi and BoA" you win big. But again, that's moving towards roulette odds, which is a good sign, even if bank failures don't bode well.
Nationalization or some other process where the stocks go to 0 is the likely end state. I'm interested in Mankiw's thing where you wipe out the old equity holders and turn a bunch of the bondholders into the new equity holders, thus recapitalizing the banks and avoiding the Japan-style zombie scenario where you have a bunch of insolvent banks failing to do the useful things banks do and eating people's brains instead.