Since launching in May 2012, more than 1 million users have uploaded over 8 million secrets to the app, Whisper co-founder Michael Heyward said last month. 

The number of whispers uploaded each week is in the high seven figures, up more than 150% since launching on Android, Heyward said.

We first thought Whisper mostly appealed to college students and teenagers, but it turns out that many of its users are also in the military, including thousands who are actively serving in Afghanistan.