Apple reports that iOS apps downloaded from the App Store have now totalled 100 billion. Considering that 1 billion devices have been sold that is on average 100 apps per device. And considering that there are 1.5 million unique apps on the Store that is an average of 66,667 downloads per app.
Personally, I have downloaded at least a thousand apps on two owned devices. So I guess I am downloading five times more than the average person. Yikes.