Users of PD2 maphacks face several risks:
Maphacks generally function by reading the memory of the game client running on the computer. The game client receives data about the map and entities from the server. The maphack intercepts this data and renders it visually for the user, often by overlaying a window on top of the game or injecting code to draw lines and shapes directly within the game engine.
The most immediate consequence is that it gives users an unfair advantage over other players. This can ruin the gaming experience for those who prefer to play fairly.
The debate over maphacks in PD2 often centers on whether they are a necessary "feature" or a game-breaking cheat: