By coiling the speaker wire, you can effectively turn your speaker cable into a nice little antenna, making it more susceptible to radio frequency (RF) interference from nearby transmitters (taxis, ham radio, whatever) of any sort. By the way, if you do get that kind of interference, you can sometimes tune it out by coiling and rotating the coiled cable until the offending RF signals are inaudible.
Coiling the cable may also make it more likely to pick up AC hum fields from your AC power cords to the equipment. To keep everything correct, the speaker cables should cross AC supply cords at right angles, not be parallel to them.
Axiom Resident Expert