Didn't expect to see a thread like this while reading about Everton. Anyway, as a Packers season ticket holder I think I'm qualified to add my two cents.
The whole notion that a Packers game wouldn't sell out is very surprising, considering that they've sold out 319 home games in a row. There are a few reasons that the streak was in jeopardy for the playoff game.
First, the offer for season ticket holders to purchase playoffs tickets is usually sent about a month or so before the end of the season. At that time this year, it looked very unlikely that the Packers could make the playoffs, because they would need a lot of things to go in their favor in order to sneak in (turns out that's exactly what happened). Therefore many fans simply didn't order the playoff tickets because they thought it would be pointless.
The next factor relates to the issue above - when season ticket holders are given the option to purchase playoff tickets, they have to pay for them up front, a month or so before the end of the season. In previous years, if the team failed to make the playoffs or wasn't in a position to host a home game at the end of the year, the ticket holder's payment could be refunded, or simply put towards next season's tickets. This year, for whatever reason, the team did not offer the refund option. They only said the payment would go towards next year's tickets. Therefore some people were hesitant to buy tickets if there was no possibility of a refund, partially due to the holidays putting a squeeze on people's wallets and people not wanting to tie up that money if they didn't have to.
The third reason is the weather. It's going to be cold. Absurdly cold. Like starting at -5 degrees (F), or -20 degrees (C), and even colder when the sun goes down and the wind chill factor is considered. It's looking like it will have the potential to be one of the coldest football games in history. We Packers fans are as tough as anyone, but that's the kind of weather that can be straight up dangerous. Not that I'm worried about it - I've been to a few of the coldest games ever, and wouldn't miss this for anything.
All of those factors combined to make this game at risk for not selling out. Fortunately, earlier today it was confirmed that it would be a sellout. When you consider that the city of Green Bay has a population of just over 100,000, it's pretty amazing to think that the city supports a team that consistently sells out a stadium that now holds 80,750 people (after an expansion prior to this season)!
To everyone saying the 49ers will stomp the Packers... you might be right. Hard to put money on a team that's 8-7-1 vs. a team that's 12-4. But anytime you've got one of the best quarterbacks in the game, you've always got a chance. And that's why they play the games.