Non-compete clauses in employment are becoming increasingly common, even outside tech industries, according to a Business Day article Monday by Steven Greenhouse in the New York Times, link here.
Only California and North Dakota ban them. California's ban on them is credited with the success of Silicon Valley, and with the decline of the Route 128 corridor in Massachusetts that boomed back in the 60s and 70s.
But even people in service industries are encountering them, as are some college interns.
Many states regulate them lightly, and require some bona fide rationale for a clause. Back in the 70s and 80s, programmers were often prohibited from working for other companies in the same business industry, but could go to other industries with the same mainframe skills. It isn't that way any more.