Um. I'd agree with PP in that teams are definitely preparing more and you see pretty much every team come in with silent count for offense, and many of them have earplugs for the linemen so that they can't even hear the snap count if they wanted to... it is supposed to make them more focused, but can backfire.
I think there were games this year where the crowd didn't expect a competitive game, the Giants and Raiders were two of those, and frankly, even the early part of the Rams game was relatively tame, it got fired up in the mid third quarter and stayed good after that... I think the Seahawk faithful are intelligent fans and that can result in some apathy in some situations.
Finally, and the conspiracy theorists might like this, I think the NFL is giving a lot more leeway to visiting offenses. You'll see a lot more motion along the offensive line that never gets called as a false start... in the past, just a hand motion or a twitch would get a false start call, now, that doesn't happen. Before my comment seems too weird, I actually think that false starts across the league are down, which is how the Clink still leads the NFL in opponent false start penalties since 2005. The other numbers have barely changed over the last season, and we've picked up four or five. (Ridiculous by the way considering the 11 that we got vs the Giants way back when... I'm pretty sure we haven't even come close to that in eight full games!)