Every time you throw a tool, two or more of that same tool are thrown. Each of those, when picked up, can also duplicate when thrown. When you die, every tool you have is thrown, and is subject to the same duplication. The best part is is that duplicated tools are unusable. The server detects them as duplicates, and thus are immediately destroyed after one use. Add this to the few PKers that camp the spawn point and you get tools everywhere.