Los Angeles-based MediaTrust, the operator of a performance-based marketing and online advertising exchange, said this morning that it has named Keith Cohn as its new Chief Executive Officer. Cohn was most recently President and member of the firm's board. Current CEO Peter Bordes will continue to be involved with the company. Cohn was previously Founder and CEO of Bardon Advisors, and also served as President and CEO of Vendare Media, the Idealab-backed Internet advertising and marketing firm. MediaTrust has offices in Los Angeles, Ventura, and New York.