How could Snapchat better protect it's API or the data returned by that API?

After reading articles like this, I'm wondering what companies like Snapchat can do better.

What are some techniques (that would work on an iPhone) to prevent (or make it much more difficult) 3rd party apps from successfully impersonating the official app and making API calls?

Or, what can be done to the data returned by that API to make it hard to decipher by anything but the official app?