The House has passed a measure imposing a special punitive tax of 90% on certain employee compensation in response to the AIG scandal. As others have noted, this raises serious constitutional issues. Article I, Section 9, Clause 3 says simply and directly: "No Bill of Attainder or ex post facto Law shall be passed." The congressional bill being considered in response to the AIG bonuses seems to violate both those prohibitions at least in spirit.
The Constitution's Framers apparently considered (page 154) this clause to be very important in guarding against legislative tyranny, and James Madison noted in Federalist 44:
Bills of attainder, ex post facto laws, and laws impairing the obligation of contracts, are contrary to the first principles of the social compact, and to every principle of sound legislation.
Aside from the dangers to liberty from overzealous members of Congress, there are issues of priorities here. While Congress has been busy with this particular inquisition, the Federal Reserve is moving ahead with a new plan to shower the economy with a massive $1.2 trillion cash infusion--an amount 7,200 times greater than the $165 million of AIG retention bonuses.
So members of Congress should be grabbing their pitchforks and heading down to the Fed building, not lynching AIG financial managers, most of whom were not the ones behind the company's failures.