It's common in some industries, yes, but in California at least, many of them aren't actually enforceable. A company can write an enforceable NDA, but it can't be a blanket agreement. It has to clearly delineate which information is confidential vs. nonconfidential, and establish credible policies for handling confidential information.
(Since employment is at-will, a company could still fire an employee for talking about anything the company doesn't like, confidential or not. But that's a different matter from having an enforceable confidentiality agreement.)
