HBO’s inventive campaign to drum up interest for True Blood, the vampire series from Six Feet Under creator Alan Ball that debuts Sept. 7, may be a little too high concept for the average mortal. Outdoor ads and vending machines that tout a bottled drink called Tru Blood have driven consumers to the network website, where they’ve futilely tried to buy the product or locate a dealer. What they end up discovering is that the beverage — which is supposed to be synthetic blood — only exists in the drama, which stars Anna Paquin and is based on the Sookie Stackhouse book series by Charlaine Harris. “We didn’t mean to dupe people,” says Zach Enterlin, HBO’s VP of advertising and promotions. The ads also include small print that encourages vampires to “drink responsibly” and to visit “We just wanted a campaign that breaks through and resonates a little bit. It’s a testament to how true to form the ads are. Some people aren’t paying close attention.”