Reflection: By taking office in the corrupt Babylon, Daniel's example would suggest that merely being part of a system (such as capitalism) that causes evil is not necessarily sin. However, when we are aware that our actions are likely to contribute to the oppression of others, we are surely more culpable (James 5:1-6).
So we must be concerned where possible not only to buy fair trade food and clothing, but fairly traded diamonds. The best policy seems in reality to just buy as little as possible, and when we do, second hand. This is about the only way you can be more certain your actions are benefitting (when through charity shops) rather than harming others and not adding to the rapid consumption of our world's resources.
Blood diamond.