Time to be affraid?

The "unexpected" results of this week, with drops in all markets, have made investors become aware of the danger that the U.S. economic weakness can provoke.
I have always thought that if investors are real analysts with experience they can respond in an appropiate way to these incidents. However, it can easily turn into a serious problem as more an more people (not professional analysts) are becoming little investors. The reaction of these new "customers" is unpredictable; depending on their decisions they can make it worse.

It would be difficult to reach the current levels without all these little investors, and it would probably be impossible to experiment even more increases in the short term if their number does not increase. But it is necessary to control them somehow, which goes against liberal principles.

Is it just a way of controlling individuals? Why did Shangai's market suffered from the sharpest drop while it was the American economy the one meant to be weak? Is it time to be affraid?