Software patents
Software patents would be negative for most of us. In fact, even some of those who demand or defend software patents today would deeply regret it later. It would only be too late then.
Patents turn software publishing into the privilege of a few. Of course, everyone can still develop software. However, in a world with countless software patents, only large corporations are equipped to deal with the incremental costs and legal risks. Even they will increasingly take a negative view on software patents if patent inflation rages on.