my friend split his cable for internet and free tv. He heard all those stories about how the cable company can detect if you have split your cable from as far as blocks away. It seemed like a myth until one day, some guy with some device with two huge antennas strapped to his chest was knocking on his back door.
My friend had split his cable line with a very cheap splitter on his balcony. The meltling snow caused water to go into the splitter and it was sending what the technician said was horrible feedback, which was affecting the quality of internet connection of the entire block.
The technician told my friend that he could agree to remove it right there and then, or he could come back with a legal mandat. My friend kindly tossed in the garbage.
So, make sure you use a decent quality splitter.