This could be old news to some or even a re-post...but I could care-less...
http://www.ducatimeccanica.com/oil.html
Excerpt -
It could appear from this data, then, that there is no validity to the constantly-used argument that motorcycle-specific oils provide superior lubrication to automotive oils when used in a motorcycle. If the viscosity drop is the only criterion, then there is certainly no reason to spend the extra money on oil specifically designed for motorcycles. There does, however, appear to be a legitimate argument for using synthetic and synthetic-blend oils over the petroleum based products.
In short, it seems to be nothing more than a clever marketing ploy designed to enhance their products' image and separate motorcyclists from their money.