Mark Zuckerberg, Facebook
Andrew Mason, Groupon
2012 have not been good years for both CEOs, with Groupon's business model in particular under attack.
FB stock YTD down 30%
Groupon stock YTD down 80%
FB has to make big move to mobile, which they have started, late, but at least it's a major focus now.
Groupon has a business model without barriers to entry, but at least Mason keeps experimenting with new products.
Both CEOs are not mature in a traditional sense, how they act (drinking beer during conference call; wearing the famous hoodie in all sorts of places), and there's no reason to believe they have the management skills to run a major public company.
Zuckerberg has also created a dictatorship, where investors are betting on him without recourse. Massive ego at work, a danger sign.