It's a pretty well accepted theory among social sciences that a surplus of young men without access to sexual partners is highly correlated with violent activity, including war. Indeed one of the theories about why there's so much violence in the Islamic world is that polygamy (which distributes young women to old and/or rich men, leaving young men with fewer partners) and the segregation of the sexes (making it very hard for an unmarried young man to have any sort of sexual access) have helped foment unrest. Young men without the hope of starting a family feel frustrated and pent up and they turn to radical religion or warmaking as a way of releasing their energy. Yay.
So the news that China has an increasing gap between male and female populations is pretty grim. Especially considering other factors that will almost certainly lead to political friction between China and the U.S. in the relatively near future. This is another example of where traditional values (boys are better) and modern technology meet up to cause serious problems.
Japan better hurry up with the production of robotic girlfriends or there will be trouble.