In the news: Drug company data mining

Do you know what your doctor is prescribing for patients other than you? Apparently, drug companies do, according to a piece in today's NYT. Snip:

Although virtually unknown to consumers, the information has long been considered the most potent weapon in pharmaceutical sales -- computerized dossiers showing which physicians are prescribing what drugs. Armed with such data, a drug sales representative can pressure a doctor to write more prescriptions for a name-brand medicine or fewer orders for a competitor's drug.

But now a rebellion is under way by some doctors, who consider the data-gathering an intrusion that feeds overzealous sales practices among the nation's estimated 90,000 drug company representatives. Public officials are also weighing in. A vote on a state bill to clamp down on the practice is scheduled for today in New Hampshire, and similar bills have been introduced in other states, including Arizona and West Virginia.

To appease the doctors and try to stave off the state restrictions, the American Medical Association will soon give individual physicians the choice of declaring their prescription records off limits to drug sales representatives. The new measure is viewed as a self-policing move that the drug industry and the A.M.A., which has lucrative contracts with data-mining companies, hope will keep states from banning sales of prescription data altogether.

Somehow, I'm missing what the AMA's stake is in this practice. Have the docs who belong to the AMA collectively agreed to the collection of this data? Who compiles the data, and how?
Link (free reg req'd).