Clictz By Enid Burns - One in four adult Internet users in the U.S. regularly visits popular social networking sites, according to “iProspect Social Networking User Behavior Study,” a report sponsored by iProspect and conducted by JupiterResearch.

The study defines a social networking site as “one that allows Internet users the ability to add user-generated content such as: comments, review, feedback, ratings, or their own dedicated pages.” Sites such as MySpace, YouTube, and Amazon.com fit the study’s classification of social networking sites.

While one quarter of the adult online population may be considered a small segment, lacking the reach of major search engines like Google, Yahoo, and MSN, it accounts for 41 million people, according to Rob Murray, president of iProspect.

The audience visiting social networking sites is self-selecting in terms of looking for specialized sites to suit particular interests. These specialized sites deliver highly-targeted audiences.

Many of these sites target communities defined by their affinity to a vertical industry, business model, or interactive activity type, unlike MySpace and YouTube, which are designed to appeal to the mass population.

“Most marketers would far more prefer targeting a very think slice of a highly relevant audience than doing the mass marketer appeal,” said Murray.

Beyond display and sponsored listings, opportunities exist for marketers. Past reluctance to get involved in online social communities signals marketers to remain cautious. “Participation on these sites can take a couple different forms,” said Murray. “[Marketers] have to pick the right site, picking the one that most closely matches your online audience. Being very transparent in your communication is very important. Each community has its own rules of engagement; a marketer must abide by those rules.”

Consumers visiting social networking sites generally do so through direct navigation and bookmarks. Secondary is navigation through Google and Yahoo, or links in e-mail. In addition to optimizing participation on a social networking site to be visible on Google or Yahoo, marketers need to ensure “that their content is of high enough interest, quality, or value that it will serve as ‘link bait’ or ‘bookmark bait.’”

The report, conducted by JupiterResearch, is based on an Ipsos U.S. Online Consumer Panel of 2,223 individuals. The survey consisted of 25 closed-ended questions about behaviors and preferences regarding online holiday shopping, search, ISP and video, online social networking (on behalf of iProspect), and online dating. Data were weighted by AOL usage, online tenure, and connection speed, determinants of online behavior.