Smartphones are getting bigger, tablets are being used to make phone calls, and laptops bend and fold in all sorts of new ways. So, how should we define all of these device categories a year or two from now? Is anything with the ability to make a phone call a phone? Should tablets and phones be differentiated by screen size, maybe 6 or 6.5 inches? How about the line between PCs and tablets - should it be based on primary input method (touch vs keyboard/mouse) or the capabilities of the OS (file manager, multi-window support, etc)? Market research firms are going to have a tough time with these questions, and will shoehorn some devices into legacy categories where they don't seem to belong. Perhaps the most useful way to think about device categories will be based on their primary use cases: portable devices that one carries with them at all times vs productivity devices with a range of input methods and more software compatibility. There is probably another category in between them somewhere, and perhaps more categories on the edges. Time will tell, it will be interesting to see how this all evolves.