While I love futuristic ideas like those of Dyson, it seems naive to assume that because we don't see evidence of our virgin civilization's futurists' visions of advanced civilization, it does not exist. This is considering that our futurists are currently living in a newborn civilization on a geological time scale and are still grounded in their vision by science that we currently have. I'm of the opinion that we should probably wait a few thousand (or perhaps million) years before we start slapping the word "law" onto some reliable physical properties we can recreate in little Earth-scale experiments.

And since we don't know for certain whether there is advanced life or not, we also don't know what the universe would look like if there was -- perhaps the current stars we see are just a fraction of the stars that existed pre-Dyson swarming.