It was only a few days ago that many media buyers were all but dismissing the threat of a strike by TV writers, believing it would be settled before the strike deadline and that if it did happen, it would be short-lived.

It was very much wait and see. No longer.

Now, with the deadline passed and picket signs up, the mood among buyers is suddenly a lot darker.

They're not nearly as confident the strike will end quickly, and they see both short-term and longer-term worries.

Media buys on late night and daytime talk shows are already being disrupted, with those shows now in repeats, and buyers worry that ad schedules booked for daytime dramas soon will be, those shows having only a few weeks of scripts in reserve.

And while primetime schedules are expected to run relatively intact for the next couple of months, buyers worry that ratings will tumble if schedules are loaded up with reruns.

That will put a huge squeeze on inventory that's already tight, as networks are called upon for makegoods to compensate advertisers for short-falls in ratings guaranteed in this past spring’s upfront ad market. That in turn will force networks to yank inventory from the scatter market in first quarter and beyond.

“There’s an assurance of audience delivery because that’s what we buy,” says John Miles, director of investments at MediaCom.

“But the absolute pricing is a function of the quality of the mix. If the quality deteriorates we then have to make accommodations via negotiations as to what that means, whether or not they continue to be appropriate places for our clients’ businesses.”

Tighter scatter inventory will quickly lead to rising prices. In some cases buyers may simply have no choice but to ask networks to return their money.

Longer-term, buyers rightly worry that viewers will tire of reruns and unscripted shows and migrate to cable TV and newer media outlets and not come back.

“In the long run, this could be really damaging [to the networks],” says Bill Reynolds, vice  president and media director at Interpublic’s Erwin-Penland. “During the last strike in the late 1980s, the cable networks started up first-run programming. Potentially, things like YouTube could run first-run programming, which could change viewing habits.”

Buyers are quick to note that for many advertisers, there simply isn’t a good alternative to network primetime, with its vast reach. That will work in favor of the networks even through a prolonged strike.

Still, a lot of other advertisers, faced with rising prices, sinking ratings and migrating viewers, will be rethinking their media strategies with an eye to moving dollars out of network.

“Consumers will still use media, although the media used may shift,” says John Rash, senior vice president and director of broadcast negotiations at Campbell Mithun. “Advertising investment is a lagging indicator of audience interest, but the money will ultimately follow the viewers.”

Meanwhile, buyers say they have no real sense of how long the strike will last. There was a feeling last week that it wouldn’t drag on because both sides--writers and producers--had too much to lose.

Now, with neither side budging, they see it going weeks longer, even months, to the extent they'll hazard a guess.

The big dispute is over whether and how writers should share in revenues from newer forms of media, such as the downloading of TV shows to computers and cell phones and the like.

It's a particularly thorny issue because no one has any real idea how much revenue that might represent, so it's hard to come up with a formula that's going to work for either side. Writers are particularly adamant on the issue of new media residuals because they feel they've been short-changed on the formula for DVD sales, which amounts to just four cents per unit.

The writers want to get it right this time, and they appear committed to staying out until they do. On Sunday, the Writers Guild of America set aside an earlier demand for higher residuals from DVD sales to focus on new media residuals.

Says Campbell Mithun's Rash: “No one is sure how media will be consumed in the long term, so a mistake now could accumulatively cost a fortune for either side."