Home field advantage is a big deal in most sports, but I'm not sure that most soccer fans keep it in mind enough when thinking of World Cups. I remember in the runup to '06 that it was hard to temper the enthusiasm of American fans wanting to "build" on the quarterfinal run of '02 when such a thing was always going to be next to impossible given the tournament location. Simply put, nobody beats European teams in Europe. Argentina and Brazil on good days can do it, and that's it. This is why the dismal US performances in France '98 and Germany '06 weren't at all shocking. It's no coincidence that all 4 semi-finalists in '06 were Europeans, while the first time the tournament was held in Asia ('02) produced a truly wide open bracket with outsiders like Turkey, USA, S. Korea, Senegal, and Japan all making deep runs. All this is a way of saying that I think 2010 could be an exciting and parity filled World Cup. I'd expect an African team to make the semis, maybe even the finals. Also a team from CONCACAF or Asia to show up in the semis. In other words, 2010 is the real test to see if the U.S. can "build" on the '02 run, and going forward, we should keep that in mind. 2014 will be another interesting one. Since UEFA is the biggest and best confederation, anytime you take that many good teams out of their comfort zone, it opens up the tourney. I think European teams also have more "continent-wide" home field advantange that other regions. Africa is just too big and diverse and tough to travel across. Asia obviously is huge and disjointed. But going from Holland to Italy for a game is like throwing the kids in the car for a road trip from Chicago to Boston.
We already made statistics about this somewhere. And while it's definitely true that there's a notable advantage for the home team, there is hardly anything that speaks for a home continent advantage (the only real exception being the actual winner of the whole tournament). South Korea/Japan was generally a bit freaky, but on the other hand the Europeans did better in the US than they did in France - in '94, we even had more quarterfinalists than in Germany.