This is sort of the correct answer, I believe, although I think of it as the Gray Goo Solution. There's much more room at the bottom than there is at the top. As civilizations progress, the timescale that is relevant to the society gets ever shorter. Because of the speed of light limitation, this means that the relevant distance scale gets ever shorter. There's nothing to do but shrink.
Dangerous Particle Physics
LOL, someone should ban this before it's too late!
When Dangerous Particle Physics are outlawed, only Dangerous Particle Physicians will have... Oh, never mind!
I like the "gray Goo" visualization. :-)