The standard argument underlying the theorem of rational voter ignorance strikes me as more evidence for (a) academics mindlessly copying academics (including even the excellent Mark Pennington) and (b) academics ignoring the real world.
Mind you, the conclusion that voters are rationally ignorant is correct in my view, but not on account of the reasons habitually given (see "conclusion" below).
It is true, people know infinitely less than they ought to in order to make an informed choice. Hence, voting is based on nonsense. And I agree with Bryan Caplan (hat tip to Laura), who belongs to the last of three schools: (i) the first arguing that democracy works well in that it faithfully reflects the will of the people, (ii) the second school holding that democracy is not working well at all, since it is NOT faithfully reflecting the will of the people, and (iii) the third school suggesting that democracy is a bit of a catastrophe because it DOES represent the will of a highly uninformed and ideologically misled electorate.
As for my introductory propositions (a) and (b), in contradistinction to the theory, virtually no-one is making probability-based cost-benefit assessments in order to decide whether to go to the booth or not. People participate in voting simply because they have been conditioned into a number of habits that encourage them to vote.
Elections are a festival, a virtual orgy of the unthinking, including the fact that few things are less likely than finding a voter who has ever seriously thought through the pros and cons of democracy. When I was allowed to vote for the first time, voting was to me like a rite of passage, a proof of my maturity; and for a long time I did think that my vote mattered - vaguely following the line of reasoning, if at all, whereby my party would have no chance to win if each of its supporters thought their individual vote was not significant enough to warrant participation in the election.
People are divided in their opinion about who is going to win the presidential election. Just compare here (Obama very likely to win), here (Romney sure to win), and here (intuiting Romney will win) - the latter with an interesting link to an article on the manner polling works and fails.
Concerning the first link, I immediately concluded that Obama was very likely to win, but do the permutational options really support my expectation?
I am an uninterested and very superficial observer of the presidential election. But, again, how much gain is there in more extensive efforts at being in the picture?
Voting is simply a different form of cheap talk. You can get a big kick at very little expense. Finding out what is really going on would be prohibitively expensive and without commensurate reward, indeed depressing. It is better to dream of nicer things, as everyone else does. One votes in order to do the done thing, feel socially accepted, even important.
If voting helps you feel good about yourself, so much the better. If it does not, never mind - what cost is there involved? The rational ignorance tenet should perhaps be rephrased thus: It is rational to vote, despite being uninformed and misinformed, for it can make you achieve a desired state of mind at little expense. And since long-term consequences, indeed any kind of consequences can be made part of achieving "a desired state of mind at little expense", they need not bother the voter.
Bryan Caplan as well as his rather short, yet still too long book ("The Myth of the Rational Voter") are overrated, however I do not regret having read the book, and his main conclusion, reported above, alone is worth the reading. Mind you, Caplan seems to dream of a world ruled by economist kings (like himself), rather than representatives of 'the plebs' (i.e. people who do not know as much economics as he does). However, in his exorbitant confidence in the wisdom of economists, he comically fails to recognise the wide spectrum of divergent and incompatible views among economists and the fact that large numbers, probably the majority of them support the same irrational world for which 'the plebs' is casting their votes.