The second-largest ad holding company in the world, Omnicom Group, is in talks to acquire LBi, one of the last large-scale digital agencies, Ad Age has confirmed. The talks are in the early stages and the companies are not close to inking a deal. To that end, LBi issued a statement acknowledging talks with multiple parties are underway: "Such discussions are at a very preliminary stage and there can be no certainty that an offer will be made for the company." LBi did not respond to requests for comment beyond that statement, and neither has Omnicom. Ad Age reported last week that LBi was seeking buyers. But new reports out of the U.K. putting LBi's price at a lofty $580 million will undoubtedly throw a wrench in those…