In several fields, patenting activity is found to increase at the same time that investment in research and development in the same field decreases. Apparently, in these fields patents do not contribute to the development of technology, so apparently patents in these fields are hardly useful for society at all.
Documentation: On software: James Bessen & Eric Maskin, 'Sequential Innovation, Patents and Imitation'. On semiconductors: Bronwyn H. Hall & Marie Ham, 'Patent Paradox Revisited: Determinants in the US Semiconductor Industry, 1980-1994'