Social computing, or Web 2.0, is receiving growing attention both in academic research and in practice. Evidence suggests that a rich set of motives entice individuals to use Web 2.0. However, traditional models of IT acceptance generally do not account for these motives, and thus are not particularly adequate to explain the adoption and use of Web 2.0. Indeed, a central construct in many of these models, the ‘usefulness’ construct, exclusively focuses on performance needs. This study makes an effort to provide an improved understanding of Web 2.0 usage by offering two contributions. First, the study reconceptualizes ‘usefulness’ into ‘needs-supplies fit’, a formative construct that taps into a wide spectrum of needs. Second, relying on person-environment fit as its theoretical lens, the study develops and tests a model of user system fit that offers a complementary perspective to current models in further understanding of Web 2.0 use.