DoubleClick announced this morning that it signed up Friendster as a "high volume" ad client. the 13-million-member Friendster, one of the first online "social network" communities, has been turning about for a revenue model for a few years, and appears to have just added advertising to the mix. Previously, it had sold special sponsorships in which fictional characters related to a brand - such as characters from the movie Anchorman - were given life and let loose on the community to interact with members. Friendster first came about just when online advertising was in a perceived decline, making it difficult to gain funding from venture capitalists and others when relying on future ad revenues. That perception has been reversed.