Running Yahoo! might not be the worst job in the world, but it might be one of the most difficult and daunting. Former Googler Marissa Mayer has been tapped to take the helm of the ailing tech company, the one-time dominant Internet directory company that has since become a sprawling, directionless, and largely unliked has-been.

It took less than 10 years. Social media has grown from just a few college kids sharing who they think are the best looking kids on campus to grandparents sharing photos of their grandchildren.