In a way, GM has used this tactic in the past. Back in the day, the EV1 electric car was only available to lease, not to own. Of course, as most of us know, leasing the EV1s eventually bit GM in the arse when it went to retrieve the cars and encountered significant resistance from owners who had become attached to them. This plan seems to get around that issue, as a Volt owner will actually own his car, just not the batteries. Of course, if GM ever decides to ask for the battery packs back, owners may be left with a giant generator on wheels.