Social and mobile technologies offer users unprecedented opportunities for communicating, interacting, sharing, meaning-making, content and context generation. And, these affordances are in constant flux driven by a powerful interplay between technological innovation and emerging cultural practices. Significantly, also, they are starting to transcend the everyday lifeworlds of users and permeate the workplace and its practices. However, given the emergent nature of this area, the literature on the use of social and mobile technologies in workplace practices is still small. Indeed, social media are increasingly being accessed via mobile devices. Our main focus, therefore, here is on the question of what, if any, potential there is for the use of social media in informal, professional, work-based learning. The paper provides a critical overview of key issues from the literature on work-based learning, face-to-face and technology-supported, as well as social (mobile) networking services, with particular attention being paid to people tagging. It then introduces an initial typology of informal workplace learning in order to provide a frame for understanding social (mobile) network(ing) services in work-based learning. Finally, a case study (taken from the literature) of People Tagging tool use in digital social networks in the European Commission-funded MATURE project is used to illustrate aspects of our typology. (Contains 2 tables and 3 figures.)