Wednesday morning the CBS College Sports Network plans to announce the newest rider on the ad network bandwagon and the latest drain on remnant networks like Platform-A’s (NYSE: TWX) Advertising.com: CBS College Sports Media comprised of CBSSports.com, NCAA.com (produced by CBSSports.com), and the roughly 215 official college athletic sites operated by what used to be known as CSTV. At the same time, all CBS Interactive (NYSE: CBS) sports properties will stop selling through remnant networks—no hard number but think millions of dollars.

The vertical ad network, which CBS says would have served 10-plus million uniques in March, will sell display and video advertising on multiple platforms. The prime demo is males 18-49. March, of course, includes March Madness, which produces high traffic; one key question is how the new ad net can produce across the year and what kind of growth it can deliver. CBSSports.com GM Jason Kint tells me that CBS is launching now to take advantage of the boost from March Madness and the main site’s rebranding from CBSSportsline.

Shedding remnants: “Our remnant networks have included the major players – Advertising.com, TACODA, Specific Media, etc.  The dollars are significant – it’s a strategic decision within sports right now.” Why cut out the remnant nets? Kint explains: “Remnant networks undervalue our audience, our brand and the relationship between the two.” Creating the new ad net “preserves a network buy and also ensures a premium and trusted environment for our advertising partners. I expect more moves in this direction across major publishers.”

• March Madness On Demand Stats: 4.7 Million Unique Video Player Users; 4.9 Million Hours Served
• Updated MMOD By The Numbers: 3.3 Million Unique Users In First Four Days
• MMOD By The Numbers: First Round Viewing Exceeds All Of 2007
• March Madness: CBSSports.com Adds Highlight Mash-ups