Most of the people I know with bigger phones are women, surprisingly. Presumably they carry their phones in their purses and a 4" phone and 7" phone are about the same at that point.
I've also seen people carrying around Nexus 7s and Kindles in their pockets. It's not exactly the fashion statement of the year, but it's also not 100% impractical.
I can confirm, at least anecdotally, that the Note 2 is a big hit with Asian women. They seem to be pulling them out of their purses all the time here.
I tend to just carry my phone anyways.. I find the N7 more practical to use than my N4, screen size really helps, even commented after getting the N7 (before the HSPA version was available) that I'd love it as a phone, combined with a headset... I tried GrooveIP on it even.. though it does work, I will probably stick to what I have a couple years before doing another hardware cycle.. the N7 did convince me that a nice tablet could be done, and bought the N4.
I have no data top back this up, but I think the back pocket is the most usual place for people to accidentally drop their devices down the toilet from.
I've also seen people carrying around Nexus 7s and Kindles in their pockets. It's not exactly the fashion statement of the year, but it's also not 100% impractical.