Does anybody know when to use "fewer"?

Bill Bennett does, but he's the only one I've heard using it on radio or TV. Andy Willoughby says his 3 Step Plan people have "less worries." David Allen, a local Jacksonville talk show host says we need "less Senators" like Teddy Kennedy. What's the usage rule? If you can count them, use fewer; if not, use less. For example, you drink less milk, but fewer glasses. You buy less gas, but fewer gallons. It was such a pleasure hearing Bill Bennett use fewer one morning, that I called in to compliment him on it. A misuse like this perpetuates itself, because children hear the misuse and think that's the right way to say it. Add in the educational establishment view that it is harmful to children to tell them they're wrong and American English continues to go downhill. Of course, the way teachers are trained these days, the teachers may not know the correct usage to be able to teach it to anyone else.