Drawing upon and distinguishing themselves from domestic, public, work, and natural settings, homeless communities offer new cultural frontiers into which ubiquitous computing could diffuse. We report on one such frontier, a community of homeless young people, located in Seattle, WA, seeking both to foresee the consequences of pervasive access to digital media and communications and to prepare for its seemingly inevitable uptake. The community consists of hundreds of young people living without stable housing, often in the public, and an alliance of nine service agencies that seek to stabilize youth and equip them to escape homelessness. We examine the opportunities for ubiquitous computing in this community by, in part, developing a precautionary stance on intervention. This stance is then used to critically examine a scenario in which information about the service agencies is made public. From this scenario, and a description of the social and material constraints of this community, we argue that ''precaution'' offers productive counsel on decisions on whether and how to intervene with ubiquitous computing. A precautionary point of view is especially important as ubiquitous computing diffuses into communities that, by their social and material conditions, are vulnerable. In such communities, the active avoidance of harms and plans for their mitigation is particularly important.