In 2002, we saw the likes of France, Portugal, and Argentina fall at the very first hurdle. In 2010, Italy and France famously went out in the group stages. In 2014, even more surprises were in store as Italy, Spain, Portugal, and, of course, England didn't even make it to the knockout round.
Every World Cup begins with clear favourites and fans tend to assume they can predict how the group stages are going to play out. But in reality, the tournament always has a few shocks to share with us, especially in the early rounds. Looking at the groups, it's easy to think that the likes of France, Germany, Brazil, and Spain should ease through into the knockout round, and even England should be capable of qualifying, but past tournaments have shown us that even the big teams can't take anything for granted at a World Cup.
There's also a bit of a curse on past winners. In recent years, France, Italy, and Spain all went out at the group stage despite being World Champions at the time, so Germany might want to be extra careful this summer!