Over the past five years, Valeant Pharmacueticals (NYSE:VRX) stock is up 856%, absolutely smashing the returns delivered by the market. And the company has recently made waves by teaming up with activist investor Bill Ackman of Pershing Square to take over Allergan (UNKNOWN:AGN.DL), the specialty pharma company famous for Botox. 

In the following video, Motley Fool analysts Michael Douglass and Brendan Mathews discuss the major risks around Valeant. As Michael notes, there are concerns about the sustainability of Valeant's serial acquisition ("roll-up") strategy, its minuscule organic growth in 2013, and management's use of adjusted, non-GAAP financials. Of those things, Brendan believes that weak (or negative) organic growth is the biggest potential issue, and he suggests tracking organic growth results closely. 

Brendan Mathews owns shares of Valeant Pharmaceuticals. Michael Douglass has no position in any stocks mentioned. The Motley Fool owns and recommends shares of Valeant Pharmaceuticals. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.