Few scenarios I've seen * "uncool" work. Stuff noone internally wants to work on. * time critical - hiring takes time. * lack of domain expertise - developme

Few scenarios I've seen * "uncool" work. Stuff noone internally wants to work on. * time critical - hiring takes time. * lack of domain expertise - development isn't all equal. Ideally you want people who understand the problem domain. * quick hit stuff - want something knocked up that'll take 3 to 6 months. Not worth the effort of resource planning internally. * budgetary - typically contractors in most bigco's (that I know of) don't come from standard headcount budget. Headcount numbers are typically one of the kpi's used to measure growth. Often times one or more of these reasons conspire together to make a compelling case to go externally.