'Virtual Currencies' Power Social Networks, Online Games

When Santiago Martinez wants to give his friends birthday presents, he buys a cake or flowers or sometimes a teddy bear. But the 41-year-old, who lives on Mexico's Yucatan Peninsula, doesn't spend pesos or dollars. He buys the gifts with an online-only currency called hi5 Coins. He also doesn't deliver the gifts in the physical world. They appear digitally on his friends' online profiles on a site called hi5, which is a social network like Facebook or MySpace. "They can't eat the cake. It is an image -- the thing that it represents," said Martinez, an accountant with a wife and two kids. "You can send the feeling of that [cake] that you want to send." In any given month, he spends the equivalent of $40 in this manner. But Martinez is hardly alone...