Fed up with the unpredictable cost of health insurance for his small business, Mike Sarafolean last year made a dramatic change: Instead of picking a plan to offer workers, he now sends them to a "private exchange" or marketplace where they compare and choose their own insurance. And the amount his company pays toward coverage is capped.

The move puts his St. Paul, Minn.-based company on the leading edge of a nascent trend that could shape how more employers offer and pay for their health benefits in the coming years. It is part of an ongoing evolution in job-based health benefits that is gradually shifting cost and responsibility to workers.