Big Brother is watching. And listening, and reading. And using your purchasing and communications history to hone algorithms that predict what you will buy and click on next. Most Americans fear their privacy is eroding in all of those ways and more, the latest Allstate/National JournalHeartland Monitor Poll has found. In an era of spreading surveillance cameras, cascading revelations about government’s collection of domestic and international communications, and online advertising triggered by users’ purchasing history, the survey said that an overwhelming majority of Americans believe that business, government, social-media sites, and other groups are accessing their most personal information without their consent. Although most Americans see many benefits in the ongoing communication revolution, the poll found a consistent current of concern about the costs to privacy that come with these advances. “It’s a double-edged sword,” said Dilek Ekerman, a Southern California-based college student who responded to the survey. “If we do give out our information, there’s the risk of it not being used properly. If you don’t, it’s hard to get services