[fjtorres]

The problem is that a lot of (most?) people do both.
Whispernet/sync makes it convenient to download the apps to your PC and Phone even if you do the bulk of your reading on the device. Conversely, a lot of folks who have started with the apps have also acquired readers. Others use the apps to search the store or shop.

Given that the apps are a good way to cheaply expand access to the ebooks for family members and that it's the simplest way to DeDRM, the raw activation numbers won't be telling you much about what people prefer or use: there are undoubtedly more apps registered than ereaders but when it comes to actual, active use...?

Odds are Amazon doesn't know either.