The carbs do account for metabolic syndrome (a somewhat out-of-fashion term for the prelude to type 2 diabetes mellitus). The carbs do account for excess body fat. There are a lot of causes of fatty liver. Fructose is a particular problem because it bypasses the pancreas's natural insulin response, which collaborates with grehlin and other hormones to induce satiety. Better to simply say fructose, more than other carbs, contributes to the obesity problem.
As for the addiction issue . . . there's some evidence that carbs actually lower serum dopamine concentration, though regional concentrations in the brain may vary differently, and are likely more important. Dopamine usually spikes after satisfying and addictive urge. So addiction is probably not the right analogy.
I alluded to what I believe is a better model in the first paragraph: fructose eludes the satiety response. So you become hungry at the sight of food (the cephalic phase of gustation), and even though you eventually become satieted, the calories derived from fructose didn't contribute to the natural negative feedback relationship.
Here's a somewhat simplified feedback diagram I made on the issue, which reflects the review and feedback of Dr Todd Berstain at University of Iowa http://nielsolson.us/Haversian/2006/12/nutritional_model.htm...
The movie King Corn does a good job of explaining the economics (http://www.kingcorn.net/), and it just so happens that the corn breeds we have lead to a lot of fructose.
If you plot obesity rate over time from 1900 to now, I think you'll see a significant change in the US obesity curve around the time Earl Butz, Nixon's Secretary of Agriculture, changed the focus of farm policy toward corporate monoculture.