So far we have yet to do anything that is outside of the energy range of events that happen naturally (albeit rarely) on Earth. But the day is coming soon where we will do things on an energy scale that never would occur on Earth... when that day comes we need to think long and hard about doing things 'just because we can'.

I am hardly a Luddite, I just laughed when some people claimed that proposed accelerators could destroy the world, because it was easily shown that particle collisions of far higher energy occurred countless times naturally. But when we enter the realm of energy scales that cannot happen naturally we need to be careful.

We are already doing things that are foreign to our natural universe. Laser technology allows you to create an intensity of light of 10^21 Watts/cm^2. I doubt such intensities are reached naturally. We can cool atoms far below the backround temperature of the universe. A Bose-Einstein condensate of Rubidium atoms exists only where intelligence creates it. We are creating laser pulses that are so short that they are measured in attoseconds (a billionth of a nanosecond)... techniques allowing the possibility of creating light pulses in the zeptosecond regime have been proposed (A zeptosecond is one thousandth of a billionth of a billionth of a second- 10^-21 seconds)

I dont think any of the above developments pose a risk, I just mention them to show that we are doing things and creating conditions that (barring other intelligences in the universe) have never happened before in the universe.

All I am saying is that some caution is a good idea.