This paper contributes to the interdisciplinary theory of collective affective niche construction, which extends the extended mind (ExM) thesis from cognitive to affective phenomena. Although theoretically innovative, the theory lacks a detailed psychological account of how collective affectivity is scaffolded. It has also been criticized for its uncritical assumption of the subject qua the autonomous user of the affective scaffolding as disposable resources, abstracting away from embedded subjectivity in particular techno-political arrangements. We propose that the social motivation hypothesis, an account grounded in recent empirical and theoretical developments in psychology as well as in the classic theory of moral sentiments, will address the former criticism by explicating the basic mechanisms of human social orientation at work in collective affective niche construction. We also begin to address the latter normative criticism in mobilizing a so-called we-mode approach to collective emotion. To make these theoretical dialectics salient, we study social media as a case of collective affective niches, focusing on the impact on subjective well-being. Finally, we briefly identify promising future directions in building a normative theory of affective niche construction on the collective level.