Rare Ventures, the investment arm of rare Medium Group Inc, has acquired a majority stake in ePrize Inc. ePrize handles online sweepstakes, loyalty and incentive programs, customer attraction, targeted email dialog programs and market research. The terms of the deal have not been disclosed. As part of the transaction, ePrize has entered a service agreement with Rare Medium to provide web site consulting and development services. ePrize will be headquartered in Detroit; in the future, the company plans to open offices in New York and San Francisco. Executives for Rare Medium say they expect ePrize to become its vehicle for direct, permission-based marketing campaigns for corporate clients.