A book I read recently claimed it all came down how precisely and clearly the patent is defined and delineated.

Imagine you moved into a lush valley with a new town in it to do business. If you found all the best spots had been taken and fenced in then that would kind of suck.

Imagine now that people had secretly claimed land, and done so in a way that even they didn't know what the boundary was. "That land over there" or "the thickest part of the forest" and yet these secret, vague claims could be legally enforced. Imagine investing money to build on that land, trying your best to avoid accidentally stepping on anyone's property.

The first case is chemical compounds, it's either got those atoms in that arrangement or it doesn't. The latter is "selling shoes over the internet" and other alleged software patents.

Though having said that I think patents are still broken and lead to the promotion of some very strange behaviour in the medical field. But in software they are appallingly bad.