My radio has been playing an ad for a car dealership that claims to measure its success by "the amount of cars we've sold and the amount of people we've made happy." FAIL! You cannot make any amount of people happy, only a number of them. And you can only sell a number of cars.
All morons who do not understand this simple concept, pay attention. I'll try to put it in very simple terms. If you can count something (One, Two, Three...) or someone could ask you how many of that something you have, you quantify it by number. For example, you can speak of the number of chicken wings you ate last night, the number of girls who turned you down for a date, or the number of raccoons that have taken up residence under your porch.
If you can measure something, by volume, weight, or other such quantification, you should speak of it as an amount: the amount of money in your pillowcase, the amount of Pabst Blue Ribbon in your fridge, the amount of lead paint you ate as a child, and so forth. Can someone ask you how much of something you have, as opposed to how many? If so, tell them the amount. This type of quantity can be converted into the numerical type by expressing the amount in terms of discrete units, e.g., how many dollars or how many cans of PBR. This is usually a more awkward expression, however. And please don't ever talk about the amount of dollars you have (remember, counting!) It's number of dollars, amount of money. Most of all, don't ever tell me about the amount of people to whom you've sold cars.
Good. That's been bugging me.