Interesting article mate, but not really surprising.
Obviously the hackers are going to target the most popular messenger programme, just like they did with IE. However, I still think if people would be sensible, then the chances of getting hit with malware, would be drastically reduced or ruled out altogether.
I hardly ever use MSN myself, but I`ve been using YM on a regular basis(every day) for a number of years and have never had an infection of any kind.
I know I don`t have to preach to you about most if not all malware attacks being down to user error, sadly, some folks will never learn.
Regards Howard