This reads like a hit-piece against ZipCar. The author doesn't give any advice, and merely retells a few anecdotes about people being stranded by parking a ZipCar in a place with poor cell service.
This isn't a problem I'd thought of before, but with the title "How Not to Go Off the Grid", I some advice. (The author doesn't even seem to offer the somewhat-obvious conclusion of "don't park a ZipCar somewhere without any cell service".)