Departing from Bennett & Segerberg’s (2013) notion of personal action frames, this paper investigates how ad-hoc networks tend to allow for a more individualised form for engagement than established organisations, and what the implications are of this individualization. The paper is based on around 90 Swedish Facebook groups and pages, belonging to both established civil society organisations and ad-hoc networks, all aimed at aiding refugees during September-December 2015, containing about 9 000 posts. We analyse the content and frequency of posts, as well as interactions, and the overlap between different groups, especially uncovering differences in organisational dynamics and mobilising power, using qualitative and quantitative content and network analysis. Our study shows that affordances of networked individualism (Castells 2007) and partial organisations (Ahrne & Brunsson 2011) create fast and large-scale mobilisation of individuals, but also creates instable and sensitive mobilisation, resulting in less sustainable organising. Ad-hoc networks harness the need of individuals’ to manifest altruism without requiring long-term or systematic engagement, thus in some ways targeting the needs of the individual online community participants themselves as much as those of the refugees. The paper concludes that ad-hoc networks are more sensitive to "viral" trends in media attention, whereas civil society organisations have a stable level of engagement on a long-term scale. However, both types of organisations have a hard time to sustain large-scale individual engagement for a longer period of time. Whereas many studies concerning the 2015 refugee crisis have focused on hate speech and anti-refugee sentiments, we show that also pro-refugee online activism is heavily dependent on media trends.