TamDenholm mentioned porn kings, and I think they are a good example of the "darker sectors" driving innovation. The porn industry were some of the first to provide streaming of videos for example. While they may not be the inventors, porn is often a driving force in adoption of new technology, it being a new format or a new delivery vector for media.
If porn is part of the "dark sectors of society" however, is obviously debatable.
Porn has also been somewhat instrumental in affirming individual freedom and occasionally pushing the boundaries of civil rights. Similarly, illegal p2p helped shaping a debate on the limits of current copyright legislation (which is far from over).
If porn is part of the "dark sectors of society" however, is obviously debatable.