[catdog]

> Whatsapp was not simple.

Maybe not 1-2 weekends simple but compared to 18 billion dollars the technical aspect is rather insignificant. It's a chat client hugely leveraging existing technology (XMPP, at least in the beginning), not rocket science.

> Angry Birds?

If you reduce it to the basic game mechanics, maybe. All in all it's surely not that simple.

I think Flappy Bird would be a perfectly fitting example here as it's so simple that it literally can be made in one weekend and made, if you believe the news reports up to $50K per day during the hype phase.