Hedge Funds are extensively cited as the main actors responsible for the financial crisis erupted in the latest decades. Their natural characteristic for secrecy and their fame for high propensity towards risks, together with the ample use of leverage, help to explain why these operators are often indicated as the main cause for the increase in markets: volatility and instability. The paper analyses the nature of these institutions and their distinctive characteristics: main investment strategies, performance measurement tools and typical organization structures. The second part of the work examines the advantages that both academics and professionals recognize to the hedge fund presence on the markets: improved price efficiency, increased market liquidity and, above all, continuing innovation. This part is followed by the analysis of the critical aspects that cause them to be on trial for any situation of financial market distress and turbulence. In particular, the study analyses the role of hedge funds in the present global economic crisis. The final part of the paper focuses on considerations regarding the present debate, which divides the financial community, on the opportunity of introducing specific regulation for the hedge fund industry.