The America of my time line is a laboratory example of what can happen to democracies, what has eventually happened to all perfect democracies throughout all histories. A perfect democracy, a “warm body” democracy in which every adult may vote and all votes count equally, has no internal feedback for self-correction…. [O]nce a state extends the franchise to every warm body, be he producer or parasite, that day marks the beginning of the end of the state. For when the plebs discover that they can vote themselves bread and circuses without limit and that the productive members of the body politic cannot stop them, they will do so, until the state bleeds to death, or in its weakened condition the state succumbs to an invader — the barbarians enter Rome.
If there's an argument for - and against - democracy that strikes, it would be that democracy makes it easier for the government to tax. "We're contributing to our own till" makes tax-paying far more palatable than "We're 'contributing' to their own clique." Ironically, this meant latent tax resistance kept taxes low in monarchical states. Had I had a chance to visit the Starship Troopers world made real, I'd expect tax rates to be low for a similar reason. Just because rich non-veterans are part of the voteless mob doesn't obviate their clout in other arenas that touch politics.
Of course, the classic argument for democracy is that it nips revolutions in the bud by providing for a peaceful change in government. That scenario hasn't aways played out, but it tends to be shakiest in new democracies - and dependable in new democracies.