American Express says that they’ll start disclosing information on their donations to 501(c) groups (trade associations, political 501(c)4s and so on) that engage in political activity, provided that the groups disclose this info to Amex:

Beginning for payments made in calendar 2008, American Express will request information regarding political contributions from trade associations, entities organized under section 501(c) 4 of the Code, and other tax exempt organizations that engage in non-deductible lobbying and political expenditures under Code section 162(e). For any such organization that receives in excess of $50,000 during the calendar year from the Company, American Express will request that the organization identify the portion of American Express’ payments used in connection with participation or intervention in a political campaign on behalf of (or in opposition to) any ballot initiative or candidate for public office, as defined under Subsection 162(e)(1)(B) of the Code. American Express will include in its political contributions report on its website any responses American Express receives to such requests.

If I were in American Express’s shoes, and making contributions to these organizations, I think I would be insisting on responses.