David Kravitz (Blue Mass Group) -- a very smart appellate lawyer and a former law clerk for Justice Sandra Day O'Connor -- writes on the subject. The most recent case I know of involving bills of attainder in the business law context is Consolidated Edison Co. v. Pataki, 292 F.3d 338 (2d Cir. 2002), which struck down as a bill of attainder the following New York statute:
§ 1. Declaration of legislative findings. The operator of a nuclear generating facility has a high duty of care to protect the health, safety and economic interests of its customers. Rate regulation of nuclear operators should discourage the taking of risks with regard to potential threats to public health and safety.
By continuing to operate steam generators known to be defective, and thereby increasing the risk of a radioactive release and/or an expensive plant outage, the Consolidated Edison Company failed to exercise reasonable care on behalf of the health, safety and economic interests of its customers. Therefore it would not be in the public interest for the company to recover from ratepayers any costs resulting from the February 15, 2000 outage at the Indian Point 2 Nuclear Facility.
§ 2. With respect to the February 15, 2000 outage at the Indian Point 2 Nuclear Facility, the New York state public service commission shall prohibit the Consolidated Edison Company from recovering from its ratepayers any costs associated with replacing the power from such facility. Such prohibition shall apply to any such costs incurred until the conclusion of such outage, or incurred at any time until all defective steam generation equipment at the facility has been replaced, whichever occurs later. Such prohibition shall apply to automatic adjustment mechanisms as well as base rates or any other rate recovery mechanism. The commission shall order the company to refund any such costs which have been recovered from ratepayers.
I can't say anything beyond that, since I'm not an expert on bills of attainder, and unfortunately don't have the time right now to get up to speed on the subject.