As an objective observer I really am having a hard time envisioning Seattle losing a single game at home. Yes, theoretically the 49ers are a good enough team to do it. Then again... 42-13. So I doubt see that, either. Otherwise, you take a relatively easy home schedule (49ERS, RAMS, CARDINALS, SAINTS, BUCCANEERS, VIKINGS, TITANS, JAGUARS), the most effective and vociferous "12th-man" in the NFL, and a supremely talented team and you've got one that shouldn't- and probably won't- lose a single home game all year.
The 49ers appear to have the scheduling advantage because San Francisco gets to face the two best teams in the AFC South at home (the Texans and Colts), while the Seahawks have to go on the road for those two contests. But Seattle, all things being equal, is a superior team to both Houston and Indianapolis and could still beat both, even away from home. But at home? Seattle is absolutely invulnerable- I don't expect a single home loss in 2013. If they get past- or once again trounce- San Francisco... there shouldn't be any other potential stumbling blocks.