Stewart Butterfield (born Daniel Stewart Butterfield in 1973) is a Canadian-born entrepreneur and businessman. He co-founded the photo sharing website Flickr and its parent company Ludicorp with then-wife Caterina Fake. In March 2005 Ludicorp was acquired by Yahoo!, where Butterfield continued as the General Manager of Flickr until he left Yahoo on July 12, 2008. In 2009 Butterfield founded gaming startup Tiny Speck, which launched its first project, Glitch, on September 27, 2011.

In 2005, Butterfield was named one of Businessweek's Top 50 Leaders in the entrepreneur category. He was also named to the MIT Technology Review TR35 as one of the top 35 innovators in the world under the age of 35. In 2006, he was named to the Time 100, Time Magazine's list of the 100 most influential people in the world. In the same year, he appeared on the cover of Newsweek magazine.

Butterfield was educated at St. Michaels University School in Victoria, British Columbia. He received a B.A. in philosophy from the University of Victoria, and a Master of Philosophy from the University of Cambridge, where he specialized in the philosophy of biology, cognitive science, and the philosophy of mind. In November 2008, Butterfield received the Legacy Distinguished Alumni Award from the University of Victoria.

Caterina Fake is an American businesswoman and Internet entrepreneur, best known for co-founding the websites Flickr and Hunch.

Fake was born in Pittsburgh, Pennsylvania, to an American father, and a Filipina mother who is a naturalized citizen. Fake graduated from Choate Rosemary Hall, attended Smith College, and graduated from Vassar College in 1991.

In the 1990s, Fake was Art Director at Salon.com, and heavily involved in the development of online community, social software and personal publishing.^{[citation needed]}

In 1997, she took a job managing the community forums of Netscape.

In the summer of 2002, Fake co-founded Ludicorp in Vancouver with Stewart Butterfield. The company developed a massively multiplayer online role-playing game called Game Neverending. The game did not launch but Fake and Butterfield started a new product called Flickr that became one of the world's most popular photosharing websites. Flickr was then acquired by Yahoo! in 2005. Flickr became part of a vanguard of so-called Web 2.0 sites, integrating features such as social networking, community open APIs, tagging, and algorithms that surfaced the most popular content. After the acquisition, Fake took a job at Yahoo!, where she ran the Technology Development group, known for its Hack Yahoo! program, a stimulus to innovation and creativity, and Brickhouse, a rapid development environment for new products. Fake resigned from Yahoo on June 13, 2008.

Cal Henderson (born Callum James Henderson-Begg on January 17, 1981) is a British computer programmer and author based in San Francisco. He was educated at Sharnbrook Upper School and Community College.^{[citation needed]}

He's best known for co-owning and developing the online creative community B3ta with Denise Wilton and Rob Manuel; being the chief software architect for the photo-sharing application Flickr (originally working for Ludicorp and then Yahoo) and writing the book Building Scalable Web Sites for O'Reilly Media. He's also worked for EMAP and is responsible for writing City Creator among many other websites, services and desktop applications.

He is color blind, and has worked on applications to make the web more accessible to the color blind.

Cal's personal website currently describes him as Glitch Engineer.