I was just (again) hinted towards this. Unlike commenters predicting tired arms alone, I can see a purpose for such input. Not on the spot, to be honest, but as a researcher I could definitely come up with a scenario in which this is useful.
Now take a short look on the Buxton Collection. You can see a lot of old “freaky” input methods. Chording keyboards, very special purpose mice & joysticks, weird wrist watches… A lot of that was not suited for the work that was/is done on the PC in general. Little of it stayed around or didn’t change much. Sure, you can claim that big old IBM enforced the keyboard (and a little later the mouse, when windows became the leading OS), but my personal guess is that this is not the only thing.
A lot of research has focused on making mouse & keyboard work well. There’s entire workshops at CHI to discuss text entry (and keyboards are still a big part of that). When I was younger (as in “younger than I am now”… geez, I’m far from being an old geezer 🙂 ) it was more of a question what kind of keyboard and mouse you bought. Not what kind of device in general. From what I see in the industry (not research!) these days, it looks like they desperately try to find new markets in that area, i.e. add a third must-have input device. Such third device is not a bad thing, I’d say, if it’s providing a benefit in certain areas (WACOM tablets). If it then also provides an efficiency boost in general, great! Chances are, however, that you will still want a keyboard when entering text. Just because the keyboard was used for virtually every task (at least partially) so far, doesn’t mean that a new technology that replaces it in one work domain has to and can replace it in every aspect!
Exactly this strikes me as odd, then. The frequent tendency to replace the standard input we’ve had so far in a desperate way. At least the ads give that feeling. You must buy it, because you need it! It’s cool! Nobody advertises Microsoft’s surface table with “cool to sort your photos”, which is pretty much the only thing you can do with any multi-touch table as a normal person. Of course the industry probably doesn’t really believe the technology is useful for everything, because it doesn’t make sense from an economic point of view. If you really replace the keyboard or the mouse, you can’t sell them anymore!
Apple, for example, now ports more and more of their design from iOS to Mac OS. They reversed the scrolling direction, change layouts, hide scrollbars… (granted, the reduction of icons to monochrome, barely readable symbols is not coming from the iPad, that’s just a stupid idea in itself). It’s a new feature (on the Mac), so a reason to buy new stuff (in this case the next OS generation).
To sum this up (and finally refer to the stupid post title 🙂 ), I’m questioning whether the sweet spot of general computing input has been reached and what we see now is “adding stuff”. The funny thing is, that it’s a little different in this case, because I am not talking about a technology that is focused on a specific task and is now starting to try to incorporate completely different tasks, I am talking about a general technology (general purpose computing) that is weirdly trying to have the special purpose aspects it “sprouted”  replace its generality.