Here's a great article you should read - on digital dumping grounds and e-waste.
The researchers have identified four categories of e-waste:
Unintentional waste data, created as a side effect or by-product of a process, with no purpose.
Used data, which has served its purposes and is no longer useful to the owner.
Degraded data, which has deteriorated to a point where it is no longer useful.
Unwanted data, which was never useful to the computer user in the first place.