Drawing together some of the below with some comments made on NZPundit: why am I so keen for people to get out there and make their opinions known?
Simple: despite everything I think about the proper role of the state and the relationship between the state and the individual, the underlying basis of politics (the "facts on the ground", as it were) is ultimately Hobbesean1. The social contract does not end the war of all against all - it merely outlaws force and the more obvious forms of coercion2. This has the effect of moving our struggles into different battlegrounds - such as politics, civil society, and the market.
Liberal democracy is one way of providing a battlefield where people don't get killed - and I think its a good one. However even in a liberal democracy, great swathes of social, political and ideological "territory" are still up for grabs, undetermined by anything other than a naked clash of interests between disagreeing parties. And where a clash of interests is involved, you've got to be in to win. If you want other people to take your interests into account, you have to let them know what you think.
I regard it as axiomatic that if you are unwilling to advocate for your interests and in consequence get walked all over by people who do, then you have no-one to blame but yourself.
So: participate or perish. Vote. Advocate. Organise. Outsource, if necessary. But whatever, make sure that your memes are in the pool and that people know you care - because people aren't always going to be polite enough to ask.
1 I say "Hobbesean" because he is the key thinker here, identifying the key problem: one of power and a clash of interests. While Locke identifies a far better solution to the problem than Hobbes' absolute Leviathan, and rightly puts the focus on "the consent of the governed", he muddies the waters of the State of Nature by trying to stick God and Christian morality back into it...
2 Here I am using "social contract" in its weakest sense, of a widely shared consensus against using force and coercion, imposed on those that don't agree by force and coercion. I'm also using "interests" very broadly and abstractly, to encompass beliefs about how things should be done, "moral interests" and such - "advancing your self-interest" can here mean working in the cause of unselfish memes.
Update: Added link to Thomas Hobbes.