Players of the social game Farmville sent 500 million Valentines over 48 hours this past weekend, the Gigaom blog reported. The valentines were free, but players pay for a lot of other virtual goods. Engage Digital Media recently released 2009 figures for “virtual goods-related investments,” showing that “more than $1.38 billion was invested in 87 virtual goods-related companies,” triple 2008’s figure. In a more in-depth story, the BBC reported that most of the virtual economy’s momentum is in social games, not so much social network sites (though some social games, such as Farmville, are found on social-network sites). “In Asia, sales are already around the $5 billion mark and rapidly growing.” The BBC piece describes how this economy works.