It's thought that Einstein once said, "If the bee disappeared off the surface of the globe then man would only have four years of life left." It seems that the fate of bees and the fate of man are closely intertwined (no surprise to us beekeepers). So if too much simple sugar is bad for man, may it also be bad for bees? Some research suggests that the honeybee's natural bacteria levels are thrown off by the introduction of sugar into the beehive. This may further suppress the bees' already weakened immune system, thereby making them even more susceptible to pests and disease. All the more reason to feed bees their own honey and not sugar, again, if at all possible.
A simple rule-of-thumb, nature's way is the best way. I don't know if it's true, but I like it.