Sorry for the lack of clarity on my part. Allow me to try again.
People may feel pressure to give blood for a variety of reasons. McGreevey's case would be a prime example. As Governor, he would be expected to participate in things like blood drives and it would be highly noticable if he refused for health reasons.
The confidential opt-out bar codes allows the donor to avoid the problems that may be associated with opting out publicly while still ensuring that nobody will be injured by the fact that he donated tainted blood.
Given that this procedure was available, one would hope McGreevey took advantage of it. No way to know for sure, of course, because the opt-out is anonymous.
No problem. The burden is mine. I just wanted to be sure I understood what you were saying. Thank you for clearing that up.