Online Content and Advertising: Are the Eyeballs drying up?

Old school online travel was about selling travel to people. Consumers would search, put in a credit card and end the process with a done transaction. New school online travel is about content and eyeballs. I have talked before about the "zero percenters" - sites which control none of the content on their website, instead relying on user generated content. Even more recently I spoke of the significant ad network that is now the TripAdvisor Media Network. I have also come across a dedicated ad network for travel content sites called - in a very creative move - The Travel Ad Nework. All of these sites and networks depending on eyeballs and advertisers willing to pay for those eyeballs. There is trouble on the horizon for ad dependent players. ValueClick Media (the second biggest of the independent advertising networks) pre-anounced their results last week. They are predicting revenue of $163-$164 million versus expectations of $166-$170 million. This slight miss caused the ValueClick stock to plunge 18% in one day. A few days later and the stock is down almost a third. Are the dollars chasing eyeballs drying up???

thanks to sean dreilinger from flickr for the photo