Using the Human-Artifact Model, this paper is revisiting the current implications for design of ubiquity, of use being everywhere, and technological artifacts replacing and supplementing one another. I look back on seamlessness and boundary-crossing as design ideals for these kinds of technologies. Based on the dialectical methods of activity theory, I offer an alternative analysis where seamlessness and seamfulness are considered as dialectical pairs, always in play in use and appropriation of technological artifact. Using the Human-Artifact Model, the paper offers more specific dialectics on the levels of activity, action and operation.