I may be completely ignorant here but how is Snapchat anonymous? I thought you shared content with your contact list... but maybe I'm missing something. Is it because Snapchat has no "profile" page a la Facebook?
It's not anonymous, but to the user it's ephemeral. You can make a pic, send it through snapchat, and be confident that regardless of the outcome (people loved it or hated it) they would never be able to see it again. Traditional internet forums are anonymous and static. Snapchat flips that around.
The author (moot) should revise the text as Snapchat is clearly ephemeral but not anonymous.