Also, if I'm not wrong, most of those light strings have a tiny fuse in the plug (to protect against short circuits in the light string).
All of the UL Listed X-mas tree lights I've seen this year have a fuse (or even two fuses in the case of unpolarized plugs) in the plug.
If you cut off that plug, you're eliminating a safety device that could protect you and your property if there is some sort of short ciruit somewhere in that string.
