Oh poor dark beer, always being judged by the color of its malt. Unfortunately, most people have the misconception that the color of beer is directly related to its weight. In the mind of most consumers, dark beers are rich, heavy and full of calories. And conversely, they think that the paler in color a beer is, the lighter it is in body, alcohol and calories.
via CraftBeer.com.
Yep, I am frequently re-educating people here at the store on this subject.
VERY true. Most modern IPAs are heavier and have a higher ABV than the average stout or porter. I am constantly reminding people of this in my trade.