Reports of a Yahoo program to search through customers’ incoming emails has spurred other tech companies to deny ever receiving a similar request from the U.S. government. The program involves Yahoo searching through hundreds of millions of user accounts at the behest of the National Security Agency or FBI. Privacy advocates said the government enlisting Yahoo to assist in email monitoring would be wrong. Other tech companies, including Google, Microsoft, Twitter and Facebook, denied doing anything like it. The whole issue underscores a legal gray area that the tech industry and the government have yet to clarify.”]