I would have thought that wifi would be attractive world-wide. I can only speak for myself, but I struggled to not add 3g capability to the wifi requirement. Wifi is so prolific in the areas I normally go that I've not experienced the need for 3g. At least to my mind's eye, wifi is highly desirable and precluded any consideration on my part for the PRS350/650 or other such EBR.
I still don't get why it would be a regional thing (wifi, that is).
Regarding formats, I was completely unaware of ebook formats until I began my EBR research a couple of months ago. As far as I knew, ebooks were like emusic... you d/l from the site of your choice and play back on the device of your choice. Wow, was I wrong. Well, temporarily, at least.
And then I educated myself on how to make it work like I thought it should. Which freed me up to buy the device of choice.
As to whether or not Sony is #2, it doesn't matter to me. I was just curious why some figures were considered to be guesses and others were taken as fact.