State Farm, Bank of America, and Great Lakes all have seen first hand recently how civil conspiracy class actions are shaping up to be powerful weapons for consumers alleging fraud in a variety of areas.

Courts have recently allowed certified classes to proceed in a string of cases, and a high-profile case against State Farm, the U.S.'s largest car insurer, alleging a “dark money” campaign to overturn a $1 billion fraud and breach-of-contract judgment settled on the brink of trial...