I hadn't realized that NBC was the fourth ranked TV network these days, behind not just the other two of the original Big Three TV nets, but Fox, as well:

Fourth-ranked broadcaster NBC has quietly begun reimbursing advertisers an average of $500,000 each for failing to reach guaranteed ratings levels, the first time a network has taken such a step in years, media buyers said.

Networks usually offer make-goods -- free advertising slots -- in the event of such shortfalls. But NBC has none to give. In fact, no broadcast network has much ad inventory left between now and year's end -- except for, perhaps, a handful of units the week between Christmas and New Year's, and that doesn't do much for advertisers chasing holiday shoppers.

CBS, ABC and Fox also are doling out make-goods, primarily for the first quarter. They have blamed softness on a new ratings formula, but media agencies disagree. None of the networks would comment.

The networks' problems emerged even before the Writers Guild of America went on strike November 5. The networks had enough first-run shows to get them through November, and repeats and replacement programming will not begin in earnest until January -- when their problems will likely start to worsen.

Among the Big Four networks, NBC has the most serious ad shortfall, as its primetime ratings are down most dramatically. Meanwhile, none of its new series this season have caught on with viewers. Compounding buyers' angst about NBC is the network's plan to schedule more reality shows, including "Celebrity Apprentice" and "American Gladiators."

"We're trying to understand NBC's recent moves," Starcom Entertainment exec vp Laura Caraccioli-Davis said.

(Hat tip: Glenn Reynolds, who dares invoke the Q-word!)