The almost-blackout for the Packers was a little bit of a perfect storm with regards to what happened.
1) The team sent out the initial order forms when Rodgers was hurt and the team was in their 6-game losing streak.
2) The team changed its playoff refund policy. They used to offer refunds for unplayed games and they instead changed it so any unplayed game money would go towards the STH's tickets the following year. They didn't think this would be a big deal but a lot of STHs didn't want to lock up money for something that looked fairly unlikely at the time.
3) The team clinched the division 7 days before the game was played. So all of a sudden they had 40,000 unsold tickets and only a few days to sell them.
4) The game was one of the coldest in Lambeau's history. Even if you could sit outside for that much time, it's not even safe to be driving from all over Wisconsin to Green Bay, and the Packers rely heavily on fans in Milwaukee, all over Wisconsin, and even Chicago to fill the stadium.
5) This year's Packers are one of the least competitive Packer teams in recent year.
That said, given the fact that this happened to the Packers, the NFL and its teams should be paying close attention to their ticketing policies.