Waste Accounts are accounts that are created by players merely to break the rules or purposely try to get banned. Not only are they annoying, but they are a wasted account and a waste of JaGeX's, and every player's time. It is near-pointless to report them, as a new waste account will just be made. These have also been used to advertise illegal real world trading sites and are used by the gold farming companines.
Waste Accounts are used for various reasons. Usually, the person is bored, and just goes on it to trash talk with random people. Sometimes, they scam people, knowing if they get banned, they only lose a low-leveled account.
However, Jagex has started to respond by starting to ban the players' other accounts, including their main account.