Are you sure they've lost 76% of their value?
Do they mean stock value, or bank + assets value?
It sounds wrong, especially since the 3DS is doing great and should have kept the value up (maybe not the stock value, but whatever).
I don't think Ninty am doomed.
Value in the stock market.
A company's market value is determined by the price of each shares multiplied by the number of outstanding shares. While it's true that the 3DS is selling well, Nintendo's handheld sales are in a decline year over year. What's also interesting is that since 2007 when the iPhone was released, Nintendo's total yearly handheld sales (GBA, DS and later 3DS) began to decline at a rate almost inversely proportional to the sales of the iPhone.
I don't like to comment on articles like this normally, but one thing really stands out for me here: "Nintendo's business model is becoming obsolete." I think that if they realize that, Nintendo's best years will be yet to come.