The term 'cloud computing' has shot into prominence recently, driven, as most buzzphrases are, by marketing interests. The term encompasses multiple, pre-existing services, but an analysis of the phenomenon's key features shows that it includes some new developments. Those developments have potential user benefits. They also embody risks. Those risks will be almost entirely borne by users and their customers, and their impacts could be considerable. Where cloud computing is being considered for nontrivial applications, careful risk assessment and risk management are essential, for organisational and individual users alike.