From the Foreword to Brave New World:

Nor does the sexual promiscuity of Brave New World seem so very distant. There are already certain American cities in which the number of divorces is equal to the number of marriages. In a few years, no doubt, marriage licenses will be sold like dog licenses, good for a period of twelve months, with no law against changing dogs or keeping more than one animal at a time. As political and economic freedom diminishes, sexual freedom tends compensatingly to increase. And the dictator (unless he needs cannon fodder and families with which to colonize empty or conquered territories) will do well to encourage that freedom. In conjunction with the freedom to daydream under the influence of dope and movies and the radio, it will help to reconcile his subjects to the servitude which is their fate.