The "featured" and "promoted" video slots on YouTube aren't for sale, according to the company's editorial policy. But a recent article at Silicon Alley Insider suggests otherwise.

According to Michael Learmonth of Silicon Alley Insider, numerous unnamed advertisers have reported that the "featured" and "promoted" video slots are routinely sold as part of advertising buys on the site, a claim YouTube denies.

For its part, YouTube has long maintained that its editorial policy, which determines the videos that play in those high-value slots, uses an algorithm from a pool of videos. That pool, according to YouTube, includes "users, partners and advertisers." However, it's not clear how much of the pool includes advertisers.

But if the allegations of payola are true, they don't seem to have helped YouTube, which is struggling to find a monetization model that works. According to a Wired report, YouTube is able to monetize only about 3 percent of its inventory. Rival Hulu claims that it monetizes all of its inventory. When one considers domestic ad sales alone, Hulu and YouTube aren't that far apart in terms of revenue, although YouTube is the clear leader when you factor in the international sales.

In the meantime, YouTube is reportedly working on expanding the banner ads on its homepage, which many consider to be the company's chief asset.