Sebastian is the founder and CEO of Tertulia, a book discovery platform that delivers personalized reading recommendations and lets readers buy books directly in-app. Sebastian introduced a co-op ownership model that gives Tertulia members a partial equity stake based on their reading and purchasing activity, a novel approach to building a community-owned consumer product. Its author services platform that launched in 2025 has already grown to 8,500+ paying subscribers. Before Tertulia, Sebastian co-founded Artsy, the art marketplace supporting thousands of gallery, auction house, art fair, and museum partners, where he served as President and COO for nine years. Earlier in his career, he spent seven years as a software engineer at AT&T Bell Labs, where his patented, prize-winning work on network optimization saved the company hundreds of millions of dollars. Dan first met Sebastian in 2012, when both spoke at the International Art Industry Forum in Vienna, Austria. Dan and James are angel investors in Tertulia.