One place you might see a rotary viscous damper in a mass produced application is in a vehicle. The handles inside the passenger cab above the window usually incorporate a torsion spring loaded rotary viscous damper.
This application is not a mission critical device. The purpose of this application is to keep the handle from snapping up and stressing the headliner and causing noise. It also makes for a classy feel to the passengers. Although automakers watch every penny in the cost of a vehicle, this is one frill they can not do without. I think it is a nicety and could probably be left out. We can discuss more applications in the coming weeks.