My personal opinion is that the double team can be effective if used in the right circumstances. What I've seemed to notice is that if the team you're playing all have high IQ's, your more likely to get burned with the DT (i.e, the DT'd player will just pass out of the DT to an open player, who, with his IQ also, will know what to do with the ball causing some serious damage to your defense). However, if the other team's IQ's are low or just average, it can be effective then (again, just personal opinion). Of course, your team's IQ's and ratings come into play also, so you have to pick your spots carefully. I don't like to use the double team that often, usually only when one, or maybe two, of the opposing teams players have the lion's share of the distro. Even 20% might not be high enough for me to DT. And if I do DT, then I generally use the "If leading scorer" option instead of the "Always" option.