There are too many variables involved for us to supply a straight, hard numbers type answer. Rider weight, rack type, terrain, cargo weight distribution, and more all come into play. Very generally speaking, we feel comfortable with combined rider and cargo weight of up to about 300lbs/136kg. However, if you're 150lbs (68kg) you probably are not going to like the handling of a bike carrying 150lbs of stuff, so be reasonable.
The Big Dummy can haul more because it is awesome. And our Trailer can haul about 300lbs give or take.