It was a year ago, and I didn;t pay all that much attention at the time, but so far as I remember, the piece of "art" was not the light bulb, but the whole room being plunged into darkness then filled with light at regular intervals. The light bulb was, of course, an essential elemant of the piece, but was not intended as the main focus.
I believe that the artist was making some sort of "statement" that word again with the alternation of light and darkness.
Personally, I considered it to be pretentious drivel, but that is my own, subjective view and I will defend to my last breath the right for any one to make an arrangement of that sort, with some "artistic" purpose in mind and to declare it as art.
I will also defend the right od all of us to say that it doesn't appeal to us and to totally disagree with the judges of the Turner Prize.