YouTube has not publicly stated that it plans to add pre-roll ads to videos. But in a BBC interview after announcing YouTube's plan to start paying video contributors, YouTube co-founder Chad Hurley said the site may begin running three-second spots before videos.

That's far shorter than the standard 15- or 30-second pre-roll, but the addition of video ads would still mark a major shift for the company and its millions of fans. YouTube has built a huge following by making it easy to view and share videos. Hurley told the BBC that its new system for sharing ad-revenue was still being readied, and that it will roll out over the next couple of months. In a statement issued Monday, a YouTube spokesman said that the company is "actively exploring a variety of ways to help the community monetize content," and that it would announce something in the coming months.

Aongus Burke, senior research manager of Harris Interactive's media and entertainment practice, said in a statement that previous data shows consumers will watch commercials online to catch a TV episode they would otherwise miss. "Yet those who are accustomed to finding and watching everything for free at YouTube may have developed a different set of expectations for the site," he said.

In more encouraging findings for YouTube, almost one in three frequent visitors to the site said they watch less TV because of the time they spend on YouTube, according to the Harris Poll. And 42% of U.S. adults online say they have watched a video on YouTube, while 14% say they go to the site frequently.

Not surprisingly, YouTube has even higher reach among males 18 to 24 years old, with 76% saying they've watched a YouTube clip, and 41% visiting frequently. The Harris Poll was conducted online in the U.S. between December 12 and 18 among 2,309 adults, of whom 363 are frequent YouTube viewers.

In a separate analysis released Monday, Hitwise found that YouTube's market share among U.S. Web sites had increased 18.5% during the week ending January 27, when Google Video added YouTube videos to its index. On Wednesday, Jan. 24, the day before the expanded index went live, Google Video accounted for just .73% of all of YouTube's traffic. By the following Saturday, however, it was generating 8.7% of all of YouTube's upstream traffic, according to Hitwise.

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