In every well-characterized example, the small transport vesicles that mediate membrane trafficking between intracellular organelles are encased in a protein coat. In general, the coat proteins assemble from cytosolic pools onto the membrane and play a critical role in vesicle formation. Recent reviews have emphasized the clear similarities in the mechanisms that drive vesicle budding at distinct cellular locations. Here we focus on the diversity of solutions to an apparently related biological task. These mechanistic differences are likely to be physiologically important determinants of the diversity in form, and function of coated transport vesicles.