small airplanes are dangerous

I often worry about all the small airplanes flying around my house.
Shouldn't
they be regulated better. I mean can these guys just fly all over with out
the government knowing about it. One of my friends told me that they
can just leave and go where ever they want without telling anybody. I
think somebody should be watching them every minute because it
could be somebody dangerous in there. Why do they need those things
anyway?