I'm surprised bash wasn't able to allocate 16 exabytes, though I will accept it's a fairly large step up from having 4GB allocated. But surely your machine had heaps of memory?
Linux will let you allocate as much memory as you want. It doesn't ever return failure based on available memory. Instead if you attempt to write to memory it will then map memory and if there is none available it will trigger the OOM killer. The kernel will attempt to kill misbehaving processes.
