The ones they used ;)
Seriously, though, I make a distinction between the goal of those who wrote the constitution and the specific methods they articulated. The goal was to safeguard the rights of the goverened against the power of the government. Everything they specified was an attempt to achieve that goal. Representative democracy (OK, a republic) was simply the best moethod they could imagine for achieving the goal.
I happen to share that goal. So any actual or possible political system has to be judged in terms of how well it protects the rights of the governed. Does the current system sometimes err on the side of allowing people to do things that may not be in the public interest? Absolutely. Does this allow some individuals to intentinally "work" the system to their own ends? Sure. But every attempt to restrict potential abuses gives more actual power to the government. Power they show a decided reluctance to give back. All things considered, I'd prefer to continue erring on the side of individual freedoms than government controls.
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Microsoft offers them the one thing most business people will pay any price for - the ability to say "we had no choice - everyone's doing it that way." -- [link|http://z.iwethey.org/forums/render/content/show?contentid=38978|Andrew Grygus]