ACORN and other voter registration groups are REQUIRED to submit all signed forms to the state, even if they're incomplete, obviously fraudulent, etc. They can flag suspected forms to call them to the state's attention, but the state makes the final call over whether the voter is legitimate--which is the way it should be. Otherwise, registration groups might throw out forms based on political party or other criteria.
If "Mickey" can vote, that means he either has a fake identity, or his registration was approved without state oversight. In neither case is the voter registration organization culpable.