I'm tempted to say that any idea which could change the political landscape even in potential is going to wind up controversial if it gains any substantial momentum, even if it's not at the moment. Politics is proverbially full of people with a vested interest in the status quo, who'd have obvious incentives not to be friendly to experimental governments; less proverbially, though, it's also full of people so attached to one shiny ideology or another that they're more than willing to preemptively demonize anything which looks like it might disprove it.
A competitive government project would probably be dismissed as the pet project of a bunch of idealistic cranks for the first few years of its existence, before it returns any substantial results, but I'd expect it to meet violent opposition if it ever starts looking like, say, modified Trotskyism, or modified Objectivism, or $BIZARREIDEOLOGYOFCHOICE might actually be a good idea in practice. The worst opposition would be directed at the experimental implementation of the idea, of course, but the system that facilitated it would also catch a lot of flak.
This post is prompted by a short discussion with Wei Dai. He says:
Perhaps we should get other causes to participate/recruit on LW? Actually, why aren't they here already? We have a bunch of individuals with non-SIAI interests, but no causes other than SIAI, despite Eliezer repeatedly saying that they would be welcome.
He has a good point!
Here's my plug, for the cause I spend lots of my time and energy on, Wikimedia/Wikipedia:
Wikipedia/Wikimedia is more analogous to a software project than an ordinary charity - your money is useful and most welcomed, but the real contribution is your knowledge.
Or, more generally: create educational material under a free content licence. If it's CC-by-sa, CC-by or public domain, it can interbreed and propagate.
(Then we need to fix the things wrong with the editor experience on Wikipedia ... though the Wikimedia Foundation is paying serious attention to that as well of late. In the meantime, if you find Wikipedia too personally annoying to participate in directly, writing your own site and CC-by-sa'ing it still helps a lot.)
What good causes can you think of that are relevant to LessWrong and its community, that leverage effectiveness through rationality? (I'm thinking beyond just legally-blessed charities, right down to the "small circle of conspirators" level of trying together to get something done.) As well as SIAI, LW has previously had plugs for GiveWell. What do you spend your time, effort and/or money on?