I do actually want to give credit to this point. I have no strong feelings at all on Marissa/yahoo, but if you join a company as a CEO and it loses 90% of it's value, from a business perspective at the very least, you failed.
If you know the ship is sinking, then you should sell it right away (at 50B) then invest that in index funds, and end up with +7% each year, instead of -90% over 4 years.