@old europe,
There is no perfect political system.
You run the risk of mob rule if you put too much power in the hands of crowds. Crowds don't take the time to learn about the issues or even to get past the initial emotional (and often hysterical) response.
On the other side, of course, you run the risk of corruption if you put too much power in the hands of too few. (I won't argue this point since everyone seems to already be behind this side.)
The United States has a decent (not perfect but decent) balance. Populism has a voice in the US, as does conservatism as do business interests. It seems to me that the presence of multiple voices is a sign of health in a political system.
Representative government-- where people elect leaders who spend their time governing is a fine system that has served our country (and others) as well as any other system could.
A "real" democracy, where important policy was crafted by the whims and emotions of people, would accentuate the worst instincts of humanity.