Tech websites were abuzz this morning with news that Microsoft may be spending $1.5 billion on the coming Windows 8 marketing launch.

TechCrunch: "Forbes reports the campaign costs between $1.5-$1.8 billion, making it the largest product launch in the history of the industry."

The Verge: "It's no secret that Microsoft is planning a big marketing campaign around Windows 8, but one estimate suggests that the company could be willing to spend between $1.5 and $1.8 billion. The huge sum, reported by Forbes, would be around triple the amount that the company allegedly spent on its Windows Phone 7 launch two years ago."

The outlet cited for that estimate? Forbes. Which is kinda, sorta true.

A post on Forbes.com by Dave Einstein does indeed say that Microsoft "will roll out with a marketing campaign estimated at $1.5 to $1.8 billion." But Mr. Einstein isn't a Forbes journalist; he's a freelancer hired by data-storage company -- and Forbes advertiser -- NetApp to write for NetApp's blog on Forbes.com, part of Forbes' BrandVoice (formerly AdVoice) program, for which advertisers pay to publish posts on the site.

But, perhaps more important, where did Mr. Einstein get that estimate from, since he doesn't directly attribute it in the post to any source (and buries it in the next-to-last paragraph)? In an email to Ad Age , Mr. Einstein says the estimate comes from an analyst quoted in the post who he describes as "extremely reliable for a long time, and has been one of the best Microsoft analysts forever." Mr. Einstein also cites in the email -- but not in the Forbes post -- a blog entry quoting a Microsoft exec as saying the company had a "10-digit" marketing budget.

In other words, it's an informed guess made by a Forbes advertiser now being repeated as a Forbes fact.

This is the new, new world of media: Journalists write for brands, brands think of themselves as publishers and publishers aren't sure exactly how they fit in.