It has become the Internet’s defining business model: free online services make their money by feeding on all the personal data generated by their users. Think Facebook, Google, and LinkedIn, and how they serve targeted ads based on your preferences and interests, or make deals to share collected data with other companies (see “What Facebook Knows”).

Before the end of this year, Web users should be able to take a more active role in monetizing their personal data. Michael Fertik, cofounder and CEO of startup Reputation.com, says his company will launch a feature that lets users share certain personal information with other companies in return for discounts or other perks.