At first I thought the Instagram website was stupid because you can only do three things on the landing pages:

1. Download the Instagram app

2. Share the image on Facebook or Twitter

3. Close the page

But then I realized this was a brilliant way to get Instagram to spread.

It's singularly focused on growing Instagram, as Rishi Shah points out:

Instagram could have easily created a web based social network and asked people to sign up on the web, but they didn’t. Instead they focused on getting you to download their app. Which is pretty brilliant since Facebook already had the web based photo social network thing covered.

Well played, Instagram. Well played.