Over at The Volokh Conspiracy, Ilya Somin has a series of four posts on rational political ignorance (the first one is here, and it links to the rest at the bottom) and discuses why it exists and why it is important.

In his last post on the topic, he mentions his 2004 paper covering some recent empirical evidence for rational ignorance, which I find especially interesting because I had been searching for such a survey without much success.