With three days until March Madness kicks off on CBS, the field of 65 teams has been set and nearly all of the advertising time is sold out.

North Carolina received the top overall seed last night after winning the ACC tournament, and Memphis, Kansas and UCLA wrapped up No. 1 seeds in their respective regions.

Now, in addition to who will actually win the three-week tourney, the only real remaining question is what sort of ratings will CBS pull after months of strike-induced doldrums on broadcast.

The answer could well be high ones. With viewers eager for fresh fare amid a sea of reruns, sporting events have been popular draws this year, reversing a long trend of decline.

The Super Bowl drew nearly 100 million viewers last month, setting a record for the game.

NASCAR’s Daytona 500 was up over last year, as were the NBA All-Star game, the NFL Pro Bowl and several golf tournaments.

Also, in addition to the usual office pools and alumni support driving March Madness, this year CBS has partnered with the popular online social networking site Facebook for a new basketball-focused application. As of last week, more than 20,000 NCAA pools had been formed.

Finally, the teams themselves should help ensure high viewership for the tournaments. Traditional powers like Duke, Kansas, UCLA and North Carolina, squads with large national followings, always help boost tourney ratings, and those four have a good shot at winning.

By contrast, though improbable Final Four runs by Cinderella squads like George Mason generate a good amount of buzz, they don’t result in high ratings.

The last four years, first-week coverage has averaged at least a 5.0 household rating, second-week coverage a 6.0 or better, and the final week at least a 9.0.

Here are other essential things for media buyers and planners to know about this year’s NCAA men’s basketball tournament.

First-round games will be played this Thursday and Friday, and the tourney culminates with the national championship game on April 7.

As of last week, CBS was 95 percent sold out of inventory, with new advertisers including Chevron and Liberty Mutual. Championship game ads are selling for $1.4 million per 30 seconds.

TNS Media Intelligence forecasts that total March Madness ad sales will hit $545 million this year, up 5 percent over $519.6 million last year.

A relatively small percentage, some $25 million, will come from online ad sales, but that number is growing quickly, doubling since last year.

For the first time, CBSSports.com will not require registration for March Madness on Demand, its web video player. It will also make the player available through a number of third-party sites, including Facebook, SI.com, ESPN.com and YouTube.

While online viewership makes up barely 1 percent of total viewership for the tourney, it has been growing at a fast rate. In fact, it may also be contributing to a gigantic slowdown in production across corporate America.

Chicago consulting firm Challenger, Gray & Christmas last year released a report saying that employers lose $1.2 billion in employee productivity during the NCAA tournament, with workers logging on to watch games and check scores on sports sites.