One of the illegal practices mentioned in the CFPB press release
was not paying out a sign-up bonus:
Deceived consumers who signed up for the American Express “Blue Sky” credit card program: Consumers were sometimes led to believe they would receive $300 in addition to bonus points if they signed up for this American Express Centurion Bank program. But consumers who met the qualifications did not receive the $300. This violates federal laws prohibiting deceptive practices.
Perhaps this will help to encourage banks to honor their bonuses that they promise in their promotions.