I got my cargo bike back from Splendid Cycles and it weighs less. Well, probably not a great deal less, but during the routine tune up, they cleaned the bike–top to bottom, wheels and all. The only other time my bike was this clean (or light) was when I bought it. I am sure it weighs less with all of the mud and dried leaf residue of the year removed.
My Yuba undergoing weight reduction: http://m.flickr.com/#/photos/wittcogmbh/7337921312/