Responsible owners do not let the battery charge reach zero. The consequences are serious enough that owners with unusual usage patterns that make this difficult will go out of their way to make sure it doesn't happen. There is a strong negative financial incentive for owners to do a simple thing like plugging in the car.
Modifying the warranty means Tesla accepts financial accountability for owners' (in)actions that are beyond Tesla's control. That's a bad deal for Tesla. It could mean financial ruin if there are too many irresponsible owners.
This thing is so blown out of proportion. When I first read the blog article I was thinking it was pretty bad. Once I had some time to think about it I realized there isn't anything unreasonable about this except the price of a new battery, but that's the cost of being an early adopter.
If you let a high end sports car sit in a garage for months with a tank full of gas and then go drive it fast you are going to wreck it. It's going to be expensive to fix. That's if you can even get it to start in the first place. A responsible owner starts the car every couple weeks or has someone else do it while they are out of town. What's the difference in effort between that and plugging in a Tesla? The only difference with the Tesla is the cost of the repair.
I think this is a case of some people being ignorant of their responsibilities as owners and failing to properly maintain their cars.