Investors are spooked by those sinking 3DS projections too I think. The last time their stock dropped this much was right before they made the emergency 3DS price collapse from $250 to $169.99 just a few months after launch.
3DS will barely hit 9 million this fiscal year, next fiscal year it will probably decline even more to 7 million or so, which is getting into a danger zone situation, for the last 15 years or so, Nintendo's basically build their business on having year handheld shipments in the 12-25 million range every year.
Before that they could get by with lower handheld sales but that's because the SNES and N64 (early years) were selling pretty good.