I think the USADA should have given a grace period (USADA would have had to advertise it somehow) for the dopers to turn themselves in before the USADA notified them of the charges (this option giving them the most leniency). If they didn't turn themselves in and admit only after they were notified of the evidence, less leniency (or none at all), and then none if they fight the charge.
That way they may have flushed a few out that they had missed.