Andrew, I'm going to side with JayJ, BobB and you. BobB is right about the coax cable. The cable is called shielded cable to eliminate outside interference and shouldn't be affected by running next to the electrical line. However, any other "low voltage" lines or speaker wires, etc. can pick up stray signals from the 110V lines and give you a 60 cycle hum in your speakers. They should NOT be terminated into the same box. If you get a short in the 110V, at the box, you could end up with your low voltage lines energized at 110V. Dangerous. They probably wouldn't be energized long, because they would burn through and that could cause problems too. There might be some places where sheathed electrical cable is illegal but I don't know of any. Your electrician is speaking from his experiences but like JayJ said, most electrical lines and coax cables are within a foot or so of each other and not seperated by a stud. I've seen many of them right next to each other. Just remember that there's a difference between the coax and the low voltage lines. Hope we haven't talked you out of installing your entertainment center!