No one questioned the 49er fans' loudness at Candlestick (except Niner fans). The hater Hawk fans and just about everybody else would just complain that the stadium was a dump.
Now that the new stadium is superior to the Stick, you have your next issue -- displacement of the real fans. The fans were always South Bay like Marvin said, but now it's the $$$ guys instead of the everyman.
It would have been very interesting to see the difference in the "12s" if Seahawk/Qwest was built in 2013 instead of 2002 (or whenever it was), assuming the Hawks became strong in 2012 like they did. My guess is that Paul Allen goes the way of expensive seat licenses just like everybody else.
This is a "new stadium" thing as of the last couple of years that has undermined the essence of HFA.
Giants fans have complained that Metlife is a worse HFA compared to Giants stadium. Opened in 2010, following 6 years of competitive football under Tom Coughlin and Eli Manning with 1 Lombardi, the popularity of the team was such that they could take advantage much like everybody else (and the Jets followed suit too, themselves off a near SB appearance in 2009). They complain that the feel of the stadium is worse than the old one, but that's another story.
When you're a real diehard fan of your team, all of this d*** swinging talk means nothing. I remember watching 49ers/Bucs at a sports bar last year, and when Kap hit Vernon on the monster bomb TD, my brother & I lit up that room pretty damn loud when it wasn't loud to begin with shocking the waitresses. I'm normally self conscious about being loud and obnoxious in public places, but with the Niners, there's no other way.
I stand for every 49er game whether I'm at the game or watching on TV, even at home.
I watched "42-13" in a s*** bar in Queens, NY with my brother and cousin....hearing Beatles music while Kap was struggling on 3rd and long.....it was so terrible you had to laugh at it, LOL. Then we moved to the back where I believe we did get sound. There was only 6 or 7 people in the whole place including the bartender. We stayed till the very end, never left.
Obviously, I'm not alone in my passionate fandom.
My point is all 32 teams have plenty of these fans (I'd say look no further than all of these forum posters...it's real).....just the ones that make it to the stadiums are not always on the same page. If you took the most diehard 50,000 fans of any team, I'd bet they'd all be just as loud and passionate as the next.
The correlation that Chiefs, Browns, Packers, Steelers, Raiders, Colts, Saints fans are the most rabid probably has a lot to do with the towns they live in, and what life is like in those cities.
You look at the 49ers, Giants/Jets, Redskins, Dolphins, Bears and those cities, and you see something different. In the biggest cities of America, things are different.
It's reality, and somebody has to say it.
The Seahawks are somewhere in between, plus a nice little tweak to the acoustics doesn't hurt either.