I care. Armitage's name was conspicuously absent from almost all the MSM coverage I saw about the Plame affair, even after he was identified as the leaker. The linked article is just more of the same: innuendo-laden disinformation.
As to who knows and who doesn't know, that would make an interesting poll question. I bet that of people who had heard of Valerie Plame, less that 5% could identify Armitage as the guy who leaked her name. Most would say that Libby was responsible, then Cheney, then Rove. It was an effective propaganda campaign.