Law professor Mark Fenster has an interesting article on the nature of secrecy, where he argues that the concept of secrecy (in Government) is not binary - and in fact, in most cases, secrecy is almost impossible to maintain (regardless of the legal frameworks). Using a diverse set of American examples; the article shows how endeavors to maintain secrecy is often self defeating - either through the pure weight of the volume of people who know the information and through disjointed laws and regulations that allow for part of secret information to "leak" out.
Although based on American examples and law, there are interesting parallels to South African government's own attempts at maintaining secrecy - be it the arms deal, or Nkandla or many other examples. Based on the article, the real danger of the Information Bill, is not that ministers can seemingly make anything secret - but rather, by its very nature, that information will leak out, and the enforcement of this law is almost impossible.