Controllers of personal data must put in place appropriate technical and organisational measures to implement the data protection principles. Business processes that handle personal data must be designed and built with consideration of the principles and provide safeguards to protect data (for example, using pseudonymization or full anonymization where appropriate), and use the highest-possible privacy settings by default, so that the data is not available publicly without explicit, informed consent, and cannot be used to identify a subject without additional information stored separately.
MarginalRevolution has another great post that documents the compliance costs, especially for would-be unicorns :