Infective banner ads are not new, but it's not so common for them to come with major websites like mlb.com and nhl.com. This video shows how easily even major websites can become victims too, and how difficult it is for them to prevent it.
For a period of half a day to a day, a major bank website was hacked and serving up exploits, and installing malware. Here's a vid of that event. A higher res version can be found at http://wormradar.com /boi.mov
This is by no means anything newsworthy, but it's interesting how transient the infective website problem is. Clean one day, hacked the next, cleaned a couple of days later.