Fear of information.

2004 was a banner year for info-banning: not only were there 20% more attempts to ban books from library shelves but the federal government broke all-time records for classifying documents:

In 2004, federal officials classified 15.6 million new documents, which is 81 percent more than in 2001. Over the same period, the cost of classifying those new documents rose from $4.7 billion to $7.2 billion. These figures do not include documents classified by the CIA, as such information is itself secret.