If you run a network cable, such as for internet, right along side of an electrical line it will disrupt frequencies into the network cable slowing speeds down. Networking cables will pick up the alternate current field around the electrical line. The two cables should not be in the wall cavity, but can be on the opposite sides of a wall stud. I pretty sure on the older coax you could run them in the same conduit, but I imagine with the new HD televisions this might cause a problem with clarity.
Condo Bob was once a TV cable guy, maybe he can answer the question about coax.