The companies are not "guilty" for taking government grants. It would be irresponsible of them NOT to take those grants unless they thought public outcry would hurt their reputations and overall sales.
If you want someone to blame for government grants (to the auto industry or any other) the blame lies with Congress and the Whitehouse. You can't point the finger specifically at any one President, either; so before the Obama-bashing starts, keep in mind that the electric car grants, and others, have been going on long before he took office.
As far as the Volt goes, I don't know that anyone can say it is a *sales* failure. I think the manufacturing capacity GM claims just isn't true. They say they can make 17,000 units per year, but only 7200 sold last year. However, dealer inventory is less than 2 Volt units per dealer -- about 4000 cars in dealer inventory across 2600 participating dealers.
Dealers have been advertising that they have Volt units for sales when in fact the only ones on their lots are already committed to customers who ordered them. That's pretty wrong to not deliver the car to the customer as soon as it arrives from GM, but hundreds of dealers have been doing this because customers will come in with interest in a Volt, they see one there, and eventually they find out they need to wait their turn to get one, or buy a different car -- and of course they have plenty of other cars to offer.
All this while the NHTSA was still trying to figure out if the batteries were a fire hazard, and for a $45,000 MSRP (equipped) vehicle that really doesn't compare favorably to other vehicles in that price range, all because there are some customers with enough extra money that they can afford to buy something trendy, or they are environmentally conscious, or hope for long-term cost savings in fuel.
I think the only thing really wrong with the Volt is it should have a Cadillac logo on it and should be marketed as an environmentally-friendly luxury item, since the average joe is probably not going to have $45k to blow on it anyway. The tax credit isn't even setup for the average joe -- it is a non-refundable $7500 credit, so if your federal tax burden for the year is already less than $7500 you don't fully take advantage of it. The average family does not pay in that much federal income tax.