The rule would require that trustees of retirement accounts act as a fiduciary on behalf of the investors in the plan, rather than acting in their own self interest. The SEC is working on a parallel rule that would require that brokers also act as a fiduciary on behalf of the investors they advise.
I'd like to hear the other side of this argument. I just recently started managing our own IRA, because it just didn't pass the smell test considering the annual fees.