Torrenting is mostly associated with software or content pirating. Big companies are aware of the threat this process has to their profitability, so sometimes they employ unusual methods to fight back against torrenting.
One of these is torrent poisoning. Basically, they infect a torrent with software that then tells the company the IP of the user who downloaded the file. After this, the company might send you a cease and desist letter, or in the (very) worst case scenario, demand reparations for any damage inflicted.