Diamond has served as CEO of various media companies including Alloy, Inc (NASDAQ: ALOY), which he co-founded. Alloy owned popular teen brands such as Smosh, Clevver and Honest Trailers. Alloy was also the first direct-to-consumer youth media company, later morphing into a multi-discipline marketing unit, Alloy Media + Marketing, which Diamond was instrumental in establishing. Diamond then went on to create and lead key expansions, including Alloy Entertainment, which produced hit television shows like Gossip Girl, Vampire Diaries and Pretty Little Liars. Prior to founding Alloy, Diamond held positions in the Finance and Operations departments at the General Electric Company.