Originally Posted by Hairy Bob

LEDs can, technically, bud a plant, but the intensity of the light is very low, meaning it can't travel more than an inch or so effectively. The real world effect of this is that you would need hundreds, if not thousands of leds per plant, placed strategically aiming at the leaves and bud sites. These would require regular adjustment to account for plant growth, and the masses of effort involved just in doing this, nevermind the task of building such a lighting system, would surely negate the slight increase in efficiency that leds offer.
I speak from experience, my veg/clone setup is based entirely around a 600led droplight (kinda like a christmas tree ropelight, but with strings of clusters of leds branching off from the main wire) and it takes some looking after. I only have 2 mothers, and up to 6 cuttings/vegging plants at a time, but that's stretching it a bit and I have to reposition most of the leds every two days so that they still point at the leaves. I can only imagine how much time it would take to keep a full scale flowering op in check!