Instagram CEO, Kevin Systrom:

In the mobile context, you need to explain what you do in 30 seconds or less because people move on to the next shiny object. There are so many apps and people are vying for your attention on the go. It’s the one context in which you’ve got lots and lots of other stuff going on. You’re not sitting in front of a computer; you’re at a bus stop or in a meeting.

But it’s not just mobile apps — it’s for whatever it is your promoting. You practically need to be able to fit the what, the why, and the how into a Tweet for it to gain any initial traction.

Kevin Systrom’s 30-Second Rule for App Success