With the Ashley attack, we all could search by name for people using that site. There may be two suicides linked to that. So, if someone wanted to out all HIV-positive persons, I have no doubt someone could do it. But, we have way more info at our docs, which could also be compromised, as medical records have gone electronic. So if someone or some group really wanted to do that, they could do it regardless. It just wouldn't be as easy to get everyone. They could target HIV Clinics, which would have the most names. But, there are many going to their regular doc. Although, many docs, big clinic based or not, use the same computer systems-- which allow us access to our medical records.
Since the records are vulnerable regardless, I think I would only be concerned in a country where the government would use the information to hurt you. That's not the case here.