Taubes argues that sugar doesn't just make you fat, insulin resistant and diabetic -- it may also promote cancer growth:
As it was explained to me by Craig Thompson, who has done much of this research and is now president of Memorial Sloan-Kettering Cancer Center in New York, the cells of many human cancers come to depend on insulin to provide the fuel (blood sugar) and materials they need to grow and multiply. Insulin and insulin-like growth factor (and related growth factors) also provide the signal, in effect, to do it. The more insulin, the better they do...
“I have eliminated refined sugar from my diet and eat as little as I possibly can,” Thompson told me, “because I believe ultimately it’s something I can do to decrease my risk of cancer.” [The director of Harvard Medical School's cancer center, Lewis] Cantley put it this way: “Sugar scares me.”Me, too.
[Source]
[Update 4/15/11: Who's been keeping the lid on the evils of sugar? The lobbyists, of course.]