Greg started Infinite Illusions in 1986 while still in college at Florida State University. At the time, Infinite Illusions had specialized only in juggling equipment. He soon branched out to carry yo-yos and he started Yoyoguy.com in the late 1990s as his online face for both the juggling and yo-yoing parts of his business. Since then, he has also began carrying other niche hobby equipment such as unicycles and diabolos. Cohen also owns a retail store for the business called Lofty Pursuits.
He is responsible for introducing would-be U.S. National Master Steve Brown to yo-yoing, first hiring him as an employee at Infinite Illusions.
Despite rebuilding and then managing the World Yo-Yo Contest successfully for over a decade, Greg's handling of Worlds in Orlando from 2001 to 2013 began to garner negative criticism from many within the community. The prevailing feeling was that the contest deserved a venue with better exposure than at the Grand Ballroom of the Rosen Plaza Hotel. These conflicts were eventually resolved by the newly-formed International Yo-Yo Federation, which then took control of the contest in 2013.
Greg had also made headlines in March 2013, when he was arrested on charges of tax evasion and stealing over $39,000 USD in sales tax money. He was since released on bail after showing that an agreement for repayment had already been reached with the IRS.