Discovery shares dropped about 7.8% this morning after it lowered its financial guidance for the year – and said that it can’t predict whether the ad market will strengthen, a growing concern on Wall Street for the company and the industry generally. “There’s no question that last month that things have slowed,” CEO David Zaslav told analysts in a conference call. Advertisers “are holding their wallets closer…We can’t really tell where it’s going right now.” Part of the problem is that many buyers are waiting until the last minute to make decisions. “Some of our networks were booking on Thursday and Friday for the weekend.… The visibility is not what it’s been.”

The CEO acknowledges that his company also has had problems with its ratings – especially at Discovery, TLC and Animal Planet which collectively account for about 70% of revenues. “We can do a better job in our flagships of growing our audience,” Zaslav says. “Over the last year so it’s been relatively flat. With the right creative leadership we can really drive that.” To that end, he talked up the recent hiring of former Disney exec Rich Ross who will run the Discovery Channel beginning in January. “We have high expectations for Rich to chart Discovery Channel’s next chapter of growth.”

But Zaslav also took some jabs at Comcast’s $45B plan to buy Time Warner Cable, now being reviewed by the FCC and Justice Department. “Everyone should be concerned,” he says. “In countries where there is a dominant monopsony power [with leverage over suppliers] it creates real challenges for consumers and in many cases there’s a retraction of investment in content. When you look at Comcast, they’re in 17 of the top 20 markets, they pass 70% of broadband [households] in America with probably the best speed. It raises real issues that all of us are looking at in the business.” He said it was appropriate for federal officials to take their time reviewing the deal. Discovery’s carriage deal with Comcast expires next year and “we’ll see where it goes.” In the meantime, “all of the content players as well as the broadband players should be looking at this very carefully.”

For now, Discovery says that it plans to increase its spending on programming by mid-single digit percentages each year for the foreseeable future.