From the back cover:

Threats and Promises: HOW DO YOU TELL THE DIFFERENCE?

Take for example the "promises" inherent in computers: super-human intelligences to do our every bidding and make our every wish come true; mind links with those mechanical intelligences to give us the gift of instant knowledge-on-demand of anything that has ever been recorded or can be calculated. Computer realities that aren't just as good as everyday life -- but much, much better.

But once we have such servants civilization will no longer be recognizable, or even comprehensible to such as us. Once you mind link with that super-intelligence you will no longer be human -- you might not even be you. And the world that "you" inhabit may be nothing more than a dream in the mind of a computer.

What was once a threat will have become a promise, and what was once a promise will be some kind of... joke.