Do walkie talkie apps actually shoot to the "top"? I assume that requires massive amounts of downloads in a huge geographical region, for example tornadoes in one part of the country might only affect 20MM of 320MM people in the US. Even if there were twenty times as many people downloading walkie talkie apps, that wouldn't put them close to Facebook.

In particular, I'd love to see detailed statistics on top free apps, changes, and what causes them.