[metageek]

They're not even using the Android sharing system. The only way to share from the Instagram app is to upload to Instagram, and optionally tell it to forward the photo to one or more of the sites they support (Facebook, Twitter, Foursquare, Tumblr). If you want real Android sharing, you have to switch to the Gallery and share from there.

[andrewpi]

It's very annoying: I kept looking for the Android 'Share' button and eventually realized that it just didn't exist on Instagram.