OK, we've heard from the pros (I live to show off and have a constitutional right to fly low passes whenever I want) and the cons (the only legitimate purpose in flying is to show how safe you can be.)  As usual, I find myself in the middle.  It is perfectly safe to fly a low pass in some circumstances and not in others.  We do a particular kind of low pass every time we land.  Doing one faster has little effect on safety (assuming the pass was otherwise safe) and there is no altitude lower than the altitude when the wheels touch down.  It is certainly possible to argue that, if you are going to fly close to the ground, you should be going as fast as possible because it gives you an instant escape (upward) if anything goes wrong.  At one time in my life I occasionally went low-level sightseeing in a T-33 in Iceland.  We flew up valleys but only with enough speed to vertical out.

That said, there are times when shining your whatever is clearly dumb or worse.  You should never be in a traffic pattern under any circumstance unless you have a clear picture of where the other a/c in the pattern are and you have determined that you are not in conflict with them.  Obviously, if you can't meet this standard, you should not be doing a low pass.  Doing a low pass where you can run into power lines or towers is beyond dumb but it is not usually a problem if you are doing it down a runway.

99% of the time, it is not the airplane or the maneuver that is unsafe.  It's the pilot.  If you are the right kind of pilot, you can fly by my airport any time.  If not, I would prefer you don't come at all.