OK, so as I'm a libertarian or classical liberal, I'm not a big fan of government regulations in general. If people want to live off of Cheetos and Twinkies I doubt they are going to spend much time perusing the nutritional labels. I do think that the market would provide labeling anyway, at least to cater to the segment of the population that actually cares about what it eats, had the government not took it upon itself to force companies to label their products. I also think it is the government's job, one of its only jobs, to enforce contracts and the rule of law so that labels should not be providing willfully false data.
Anyway, if there are going to be mandatory labels, I think it would be helpful if they looked something like this:
That's the winning entry from a UC Berkeley Graduate School of Journalism contest. Obviously I have some quibbles, the low-fat high fiber agenda, etc, but that's already built into the government regulatory system's "settled science". Still, the block chart format is pretty damn cool.