A type of an online incentive to encourage users to take action on a Web site, in exchange for the ability to purchase items. For example, in January 2008, Gaia Online recorded the highest average visit time amoung websites within the social networking category. One driver of the time being spent on this site is "Gaia Gold Pieces" - virtual currency earned through interaction with the website such as posting in forums or playing games. Users can then use the pieces to purchase items for their characters. These types of currencies have been popular with virtual worlds like Second Life and Club Penguin which provide rewards and recognition for usage.