Greg Isenberg

Isenberg's first business was Stress Limit, where he ran digital marketing strategies and oversaw the web design rebranding efforts of FedEx, Microsoft, and TechCrunch. On the experience, Isenberg noted, "I learned very early on that to be competitive and do business with people, you first need to build relationships. So that meant flying out [of Montreal] regularly to San Francisco and New York City to meet them in person, tell them what we’re working on, and making them as excited as possible to work with us."

Isenberg's social media app Islands, a messaging app for college was bought my WeWork in 2019.

Upon its acquisition by StumbleUpon — their first-ever company acquisition — 5by expanded its team to thirteen employees and moved to San Francisco. Forbes remarked that, "It might be the fastest start-up to sale company in the social media technology category." StumbleUpon acquired the company with the intent of having it further monetize its mobile video aspirations and to increase revenue from its large user base.

In October 2014, 5by relaunched as a mobile app for chatting about online videos with friends. Partnerships with VICE, Tribeca Film Festival, Defy Media, and Mashable were brokered to bring verticalized content onto the platform. The shift toward social features mirrored StumbleUpon's own efforts with its mobile applications.

Greg Isenberg (born February 3, 1989) is a Canadian Internet entrepreneur and venture capitalist. He is best known as a technology startup thought leader and the founder of the Webby award-winning 5by, a video discovery platform acquired by StumbleUpon in 2013 for an undisclosed sum.