eMarketer looks at how social networkers' web behavior differs from that of the rest of the population, and examines key points to keep in mind when launching a viral campaign.

Doubtless the most famous scene in Mark Twain's "The Adventures of Tom Sawyer" is when Tom not only gets his friends to whitewash the fence for him, doing work he would prefer not to do, but he goes from being a poor poverty-stricken boy in the morning to literally rolling in wealth.

While this concept deserves an entire report (or perhaps a user-generated website) of its own, let's examine how the Tom Sawyer model best describes current and future paths for internet video, both with content and for advertising.

Social network sites, such as YouTube and MySpace, encourage video usage. You probably knew that, and the data back you up. While 55 percent of the people who visit such sites at least weekly watch streamed videos, only 22 percent of non-visitors do the same, according to a report from Parks Associates, a Dallas-based market research firm.

Take "Lazy Sunday." The Saturday Night Live clip of two guys rapping about cupcakes, red licorice candy and "The Chronicles of Narnia" movie got six million views. And while NBC demanded the clip be removed from YouTube -- some say shortsightedly -- the clip effectively promoted the SNL show without any effort from the content owner.

The "Lazy Sunday" phenomenon also depended on another Tom Sawyer element: viral communication. According to the "Viral Marketing 2006" report from MarketingSherpa, 47 percent of U.S. viral marketers cited video clips as delivering great results. Video engages, video is fun, and therefore, people want to pass along links to cool videos.

Advertising as viral video content often means scattering several versions on the web. The lower costs for viral video -- which need not be as slickly produced, and often should purposely not be slick -- make multiple messages more feasible.

David Hallerman is a senior analyst at eMarketer and this article was drawn from his report, Internet Video: Advertising Experiments and Exploding Content. Contact eMarketer directly.