the world of patents

UNITED STATES PATENT OFFICE 2,682,235 BUILDING CONSTRUCTION Richard Buckminster Fuller, Forest Hills, N. Y. Application December 12, 1951, Serial No. 261,168, p. 1.

Investigating the world of patents in conjunction with Buckminster Fuller's 1951 patent of the geodesic dome, which made him quite wealthy as he licensed the rights far and wide, I have discovered a) that patents only last 15 years and then are released to the public domain, and b) that there is a certain madness in the patent world.  
Evidently inventions must be novel, useful and not obvious.
Novel we get, not obvious means that it can't be a logical development of a previous patent, but useful?  This clearly is a wide and ambiguous quality.  

Many patents are genuine developments that advance medical technology, etc., but someone wants to put a clamp on the developments to make money from it.  Well and good, research and development costs.  Others seem to respond to some really annoying problem someone has in their daily life and god dammit they are going to solve this, patent it and make a fortune.  Such as the bird trap cat feeder, which catches sparrows and feeds them to cats. 

UNITED STATES PATENT OFFICE 4,150,505 BIRD TRAP AND CAT FEEDER Leo O Voelker, Linn Kans 66953 Application August 8 1977, US1977000822683 p.1.Now, what world does this person live in?  Is there a personality type that easily loses perspective in the blinding light of their own genius?  What is wrong with sparrows that they should be so cruelly hunted – it is something like finding out that the Elizabethan delicacy, lark's tongues, required a thousand tongues to make a single serving.  Was Elizabethan England overrun with larks?  Was Kansas in the late 1970s visited by a plague of sparrows?  

Oh no, there is a large section of google references to sparrow control.  Evidently they are invasive, successful and displace little native birds.  This is one of the discussions we are having in the contributions to On Site 32: weak systems – successful invasions of the small and insidious.