Adroll.com is not just another ad network, it's a social ad network. There's a difference. Adroll is betting that by allowing niche publishers to organize themselves together into communities with similar interests they will be able to be able to better attract advertisers by combining their traffic. This is an example of making money on the long tail, something Alex Iskold recently noted was the only effective way to make money involving the long tail. Adroll was founded by one of the members of the so-called "Paypal mafia," Jared Kopf, who is also a co-founder of Slide.

For example, when you visit Adroll, you'll notice the "Surfing Ad" community consists of 7 smaller niche surfing sites that collectively attract about 620,000 visitors per month. Smaller publishers can band together and form their own communities or join an existing community. This is not a new idea. The widly used (especially by political blogs) Blogads encourages bloggers with a similar focus to band together to increase their allure to advertisers (i.e., conservative bloggers, or liberal bloggers, etc.). Adroll is merely bringing that tested format outside of the blogosophere (further, Blogads is invite only, so a current publisher needs to get you in, which makes it harder for beginning bloggers to join).

There are three types of communities: open communities where anyone can join, member invite communities where only members can invite other publishers into the community, and leader invite communities where only the leader of the community can invite new members.

For advertisers, buying ads across an entire adroll allows them to reach a larger number of niche readers with a single ad buy. They can also purchase across a tagroll. When publishers submit their sites into the system, they setup their profiles with tags to describe the site, i.e. "sports," "stocks," and "technology." An advertiser can simply buy a tag and be shown on any site with a matching tag. The same thing applies for publishers; they can search for advertisers with tags that match their profile.

Conclusion

Whether advertisers will end up purchasing ad space depends on how many publishers join the program and whether a group of niche blogs is better for advertisers than a few large sites that get lots of traffic. Also, if publishers allow too many members into the community, it could become diluted and the niche targeting that is the site's bread and butter could lose its effectiveness. Lastly, many advertisers like to target a particular demographic, such as age, income level, location, gender, etc, but Adroll only allows advertisers to target by interest and topic.

Even so, it's still a great way for smaller publishers to join together to create a more powerful ad inventory for advertisers. Just like any other social network out there, though, only the popular publishers will get any attention.