Hybrids in general aren't commercially viable. The Volt is no different. They are marketing gimmicks. It's well known that the first generation Prius sold at a loss. Toyota's protestations to the contrary, they did little better than break even with the second generation. Adding more batteries and provision for plug-in charging is going to make the business case even worse.
To compound matters, hybrid sales have underperformed the market significantly since the price of fuel dropped from last summer's price spike. In December, Prius sales were down ~50% compared to ~30% for the industry as a whole.
More energy savings could be had with smaller, lighter cars with direct injection diesel engines, but that isn't what the American market wants. The hybrid is simply another technological solution to a behavioural problem.
I do, however have a problem with any government dictating what type of car the manufacturer should be concentrating on. It is the downside of the Faustian bargain GM and Chrysler now find themselves in.