Estimates vary widely, but they’re all bad–as we thought they would be. Variety says ad agencies think the four broadcast networks–News Corp.’s (NWS) Fox, Disney’s (DIS) ABC, GE’s (GE) NBC and CBS (CBS)–plus the pint-sized CW, may have seen sales drop by 10 percent to 12 percent compared to last year. Ad Age thinks the decline could by as much as 15 percent. Mediaweek says sales are down a staggering 22 percent.

The other bit of consistency is the explanation for the drop, which is two-pronged: Sales are down both because the economy is bad and because the networks are offering less inventory than they normally would. They’re holding back lots of their spots in hopes of selling them at higher prices later in the year, presumably when the economy comes roaring back.

I’ll let bigger brains than mine handicap the odds of that happening (but for the record, you can color me skeptical). In the meantime, let’s see what depressed TV ad prices do to prices for Web video ads.

That’s a lot of Superpokin’….

Apparently our self-righteous outrage over Facebook’s tweaks of its Terms of Service or claims that social networks are haunted by sexual predators has done little to dampen our enthusiasm for them. “Social networking has become a fundamental part of the global online experience,” said Nielsen Online CEO John Burbank in one of those “Fire: Hot, Bread: Good” announcements. “While two-thirds of the global online population already accesses member community sites, their vigorous adoption and the migration of time show no signs of slowing. Social networking will continue to alter not just the global online landscape, but the consumer experience at large.”

Unfortunately for the companies playing in the space, social networking hasn’t yet done the same for the advertising experience. Indeed, as Nielsen notes, “The current level of advertising activity on social networks isn’t consummate with the size–and highly engaged levels–of the audience.” Nor will it be, unless the sites figure out a way to exploit the personal data of their users without making them feel like their privacy has been invaded. Nielsen’s big idea for achieving that goal: trial and error. “New approaches to the ad model are required for this challenging and complex arena,” the company explains. “It will take time to work out the magic formula for successfully advertising in social networks. The diversity and personalised nature of the environment means standard ad models–such as contextual search and standard unit sizes–won’t cut it. Different approaches across ad units and ad inventory will have to be tried, involving a trial and error mindset.”

Trial and error, eh? That’s been Facebook’s strategy hasn’t it? And as I recall, it hasn’t exactly been working out too well…