I was cramped for hard drive space, so I was looking for a place where some files might have been duplicated during a restore. The culprit turned out to be root trash, but this stuck out like a sore thumb.
This Page says that the file is an alias for my memory and the size of the file is the same as the amount of RAM that I have.
Now that can't be entirely true, because I only have 4.0 GB of RAM.
What is going on here?