1 When ‘friends’ collide: Social heterogeneity and user vulnerability on social network sites Sarah L. Buglass Jens F. Binder Lucy R. Betts Jean D. M. Underwood Nottingham Trent University, UK PRE-PUBLICATION VERSION Published as: BUGLASS, SARAH L., BINDER, JENS F., BETTS, LUCY R., UNDERWOOD, JEAN D.M., 2016. When ‘friends’ collide: Social heterogeneity and user vulnerability on social network sites. Computers in Human Behavior, 54, pp. 62-72.