Shrooms are not dangerous in the sense that you can't overdose and stop your heart. However, have a bad trip and try telling me that they aren't dangerous.

A word of advice from past experience, shroomin in an arcade filled with flashing lights, weird electronic noise and hundereds of screaming kids is a really good way to have a bad trip! At the time It sucked worst than anything I had ever experienced, but I can look back and smile at it now.