In the mid 1950's the fears were nuclear war and communism (in western democracies), while in the mid 1960's new concerns entered the science fiction landscape, and others left. Look at 1984, and you will find the deep rooted fear of a British author of succumbing to a worldwide communist system based on a perpetual state of war, with the resulting absolute control over the individual that we all know now as "Big Brother".
The 1958 Space Merchants tackles new concerns, ones that in the 1960's hippie culture would play an important role, to be forgotten in the 1980's and 90's only to return in the first decade of the 21st Century: Environmentalism. This coupled with a newfound distrust of big businesses, and lack of confidence in the government of the USA, they paint a bleak future, but at the same time it's the promise of technology as the savior of mankind.
We have to remember that in the late 50's and early 60's Popular Science and Popular Mechanics were telling us that by the year 2000 cars would fly and weather would be controlled by computers and human beings would have lunar bases and colonies in Mars. These were not Science Fiction stories, they were the prototypes and promises of a brighter future brought about by scientific and technological development. Then in the 1980's something changed, and technology started to become a threat, like in stories such as Neuromancer and Terminator, where the promise of technology turned out to be a threat, a disappointment, and we needed a new paradigm.
Which do you think are the concerns we are putting into today's Science Fiction?