Alloy Media and Marketing has signed exclusive integrated ad deals with social-media startups, including avatar design firm Meez, viral widget company RockYou and urban social network Block Savvy, MediaPost writes.

Alloy will serve as their exclusive integrated advertising partner, handling all ad sales and promotional deals with marketers and agencies seeking to reach the teens, tweens and college kids using the social media. Alloy has also renewed its commitment to act as exclusive advertising partner to Habbo Hotel, another virtual community for young people.

While Alloy's nearly 1,500 partners pale in comparison to MySpace's size, smaller social networks can prove valuable to marketers. The more intimate the community, the more people participate and engage, according to new research from online community developer Communispace.

Communispace says 86 percent of the people who log on to private, facilitated communities with 300-500 members make contributions, whereas on public social-networking sites, blogs, and message boards the vast majority of visitors do not contribute. In a typical online forum, for example, just 1 percent of visitors contribute.