This chapter focuses on applying an activity theoretical perspective to platform work with the aim of better understanding the essence and developmental potential of this new and assumedly increasing phenomenon. It describes reasons for its emergence and essence, as depicted especially by Arun Sundararajan in his well-grounded book The Sharing Economy: The End of Employment and the Rise of Crowd-Based Capitalism. In the platform-based, sharing economy, new resources are incorporated into economic activities, services and products are crowdsourced, and contractors and workers may easily shift between roles. Markets are based on low-information, high-velocity transactions that tend to quicken process of transforming the object, with no necessary permanent relations. Activity concepts resemble organizational cultures in that they are not often verbally expressed, nor are people aware of them until they are challenged by changes or disruptions. The network concept has potential for enhancing both freelancers’ proactiveness and collective innovations, but network concept and its benefits seem marginal in the Upwork activity.