You whiners need to get over it. AT&T is a business and therefore it makes business decisions. When AT&T offered unlimited data, devices simply didn't use that much, they were slow, apps were slow, steaming movies and videos through cellular technology wasn't quite here yet, etc.
Now data consumption has gone through the roof and AT&T has to manage their costs. You are bunch of entitled babies that expect businesses to operate at a loss to give you the service you think you deserve. You are lucky they didn't strip away your unlimited data already. Businesses are NOT in business for the good of humanity. They are here to make a profit. They make a profit by providing goods or services at a price where we can FREELY choose to trade our hard earned dollars for that service. If you don't like the service they provide, STOP freely CHOOSING to trade your dollars for their service. It's as simple as that.
You are incorrect sir.
AT&T sells a service, that service is data. Customers should be free to do what they want with that data. If that includes making Facetime calls over 3G/4G that is their choice. They are paying for the data and they get to choose how they use it. If they go over their allotted amount, they pay overage charges. It's as simple as that.
Businesses are in the business of making money, but they still have ethical obligations. Trying to restrict the way someone uses a service they are paying for isn't ethical and that is why people are complaining.