Economists argue that it is usually rational to be ignorant, and that it is rarely rational to be well informed. This conclusion is simply the result of cost-benefit reasoning. There is a vast amount that a person could know, but a very limited amount of time to learn, so what we know is tiny compared to what we do not know. Further, most people will be poorly informed with regard to political matters because there is no clear benefit from knowing them.
Someone who does not like President-elect Obama has posted a video that is both funny and also an excellent example of rational ignorance. The site acknowledges that interviewing a few people is hardly evidence of anything, so it commissioned a Zogby telephone poll to ask its questions. The results showed that 57.4% could NOT correctly say which party controls congress (50/50 shot just by guessing), but only 6.2% failed to identify Palin as the one with a pregnant teenage daughter. The site is http://howobamagotelected.com/.
Update: More information about the poll is here.