but why? I don't understand these reactions.
Firstly, it's perfectly normal when something happens to chime in with "Hey, that happened to me too" -- especially something kind of unusual. If you keep quiet and people find out afterwards, then they think it's odd you chose to stay silent when the issue came up.
Secondly, there are conspiracy theories that the MSH breach was perpetrated by someone who is "out to get Rob" and will sell his info to his enemies, etc. Well, someone improperly accessed Jack Layton's records and -- so what? -- nothing ever came of it; we never even knew till now, we never would have known if Chow didn't choose to reveal it.
But it shows that when famous people are in hospitals, it's likely some people will want to "see" their chart -- they same way they click on the link to "see" their wedding photos or naked pics. Chow's revelation supports the idea that what happened is probably not that uncommon and that most human beings are drawn to snoop into the lives of high-profile/famous people just to scratch their curiosity itch, nothing more.