Yahoo shares are sliding on worries that Verizon will walk away or slash its $4.8 billion offer for the company's digital operations after another massive data breach. Yahoo on Wednesday revealed that information was stolen from more than 1 billion user accounts after disclosing a separate hack of some 500 million accounts in September. Verizon had said it would reevaluate the Yahoo deal after the first hack, and said the same Wednesday after the latest revelation. If the hacks drive Yahoo's users away, the company wouldn't be as valuable to the telecom giant in its quest to build a digital-ad business. Verizon spokesman Bob Varettoni did not reply to questions or messages Thursday. Yahoo shares are down 4.4 percent to $39.12 in midday trading.