This is a common problem. All home light switches arc inside them. An inductive load causes a larger spark, in most cases. Some florescent lights are worse yet. I have to change some new Leviton Decora switches (20 amp switches with just lights) with a different brand. These arc so bad everyone is afraid of them, since you could see it (flash) along the edges of it. They probably could put a capacitor inside them to lesson it, but maybe the average person doesn't care, or know the difference.
It does cause some interference through the line (shares the same neutral and secondary in utility transformer), and RF through air. Also, a little spike depending on what it's switching. I think the first wireless radio transmissions were done with a arc or spark jumping across a gap. Even the small power supply for my laptop gives a good visible arc when unplugged, and causes interference on the TV, that's on a separate phase leg. Like Almarg mentioned above, you'll probably pick it up with an AM portable radio.
I guess it's something not worth the worry in most cases. Even less of a problem, on a separate circuit. Living close to a substation like the one in this video that switches the load would probable be more annoying, at least for myself. [http://www.youtube.com/watch?v=IG7PQOQEFmg&feature=related]
