I was at a restaurant and tore off the paper napkin ring. To my amazement, I saw that it was patented, number 6644498 to be exact.
It dates back to 2001. Here's the abstract:
A continuous strip of individual napkin ring blanks that can be separated to form a plurality of napkin rings. Each individual ring blank extends between a leading edge and a trailing edge and includes a first adhesive area and a second adhesive area. A line of perforation is formed between the leading edge of one ring blank and the trailing edge of the preceding ring blank such that the ring blanks can be separated from each other. Each of the ring blanks includes a pair of angled locating surfaces formed near its leading edge and a pair of angled locating surfaces formed near its trailing edge to provide a visual indication of the line of perforation between the ring blanks.
Note that the adhesive is not part of the patent, but how it is placed is a key element:
In accordance with the present invention, the adhesive area positioned on both the front and back surface of the napkin ring is a conventional adhesive as is currently used in the industry. The adhesive area must be strong enough to hold the napkin ring in place around a set of silverware and napkin.
How can you live in America and not appreciate the genius of our patent system? I mean it. Without patent protection, this advance likely would never have made it to the marketplace. Would that have mattered? You bet.
Kevin Drum at Mother Jones also noticed this (in 2009) and explained more about its value to the world:
The patent is not for anything to do with the napkin ring itself but for the packaging method: they're sold on a roll instead of in a box. This is apparently a boon to wait staff and busboys everywhere.