Science and technology have made our lives easier, cured diseases, with achievements that an earlier age would have considered impossible. But once in a while, the law of unintended consequences breaks loose. Christopher Anvil considers the two faces of technological innovation: Sometimes the result is a literal life-saver; but at other times a breakthrough may not break quite the way it was supposed to. <P>  <P>·         A new wonder drug has the unexpected side effect of making people happy. Not a problem—everybody should want to be happy, right? But should people be happy <I>all</I> of the time? Suppose being happy required you <I>never</I> to disappoint anyone, no matter what they're requesting. . . . <P>·         Then there was the energy source for every home that would free the country from its dependence on foreign oil—except that the prototype was rushed into production a bit too fast. <P>·         Back on the bright side, another device not only couldn't possibly work by every known law of science, but didn't have any obvious uses. Then alien invaders landed and suddenly the crackpot device was the world's only hope. <P>  <P>     The upside and downside of marvelous new gadgets, as told by a master of science fiction adventure with a prescription for fun. <P>