There is nothing wrong the rule. From the perspective of someone who isn't a soccer fan and has only really watched the most recent men's and women's World Cups: It seems like an overly harsh rule to have a team play one person down when the calls can be so subjective as they pull red cards for. With the repercussions so severe (which is fine in and of itself), it seems like they should eliminate the subjectivity from it. For instance, pull a red card only on the most obviously blatant stuff and not for highly questionable calls like the one in the US/Brazil game. The Zidane headbutt, for example. That may be a flawed view, but it's what I've kind of gleaned from very little soccer experience. Straight reds are pretty much only for blatant stuff and you really don't see that many, im guessing between 5-10% of all cards issued are straight reds. Two yellow cards in the same game are much more common. At the same token, you are aware of the first yellow and should know to adjust your game and play a little bit more cautiously. Similar to playing with 5 fouls. Every player knows what they have to do to earn a straight red and with a yellow fair warning has been issued. Also refs are a little more forgiving in issuing a 2nd yellow.