Our culture informs us of what is socially acceptable (theft, greed, dishonesty etc) and meters out justice through our real social networks of family and friends. For issues that raise to a level of criminality we use the legal system.

I also think it's perfectly fine to make use of technology for selfish ends. That's the real reason competitive market economies function more effectively than command economies. When we all act out of our own self interest we buy the best value good and reward the most efficient producer. (Thiel argues with this and I admit this pattern does not hold in markets with monopolies, cartels, or regulatory capture)