Another corporate angle is the extent that MAD (Mutually Assured Destruction) is at work. Large companies in older industries will have a large portfolio and if they get hassled by a competitor, the competitor can strike back.

As a practical matter, what can happen is that small companies can't get traction since all of the minimum features/implementations in a given type of product have already been patented by one of the existing older companies as a form of low-hanging fruit.