Scott Becker explains how the AMA sold out physicians in its desire to "have a seat at the table" in the health care legislative process.
In short, the Obama administration needed their moral sanction and political cover for its agenda, and they desperately needed to be able to claim the support of doctors. The AMA sold its support for essentially nothing. Rather than having a "seat at the table", they instead put doctors on the menu.
Most physicians are not members of the AMA anyways (contrary to popular misconception). The recent ObamaCare debacle may drive more of them out, and into the arms of alternative groups such as the Docs4PatientCare.