Probably more than anything we’ve seen in IT since the invention of timesharing or the introduction of the PC, cloud computing represents a paradigm shift in the delivery architecture of information services. This overview presents some of the key topics discussed during the ACM Cloud Computing and Virtualization CTO Roundtables of 2008. While not intended to replace the in-depth roundtable discussions, the overview summarizes the fundamental issues generally agreed upon by the panels and should help readers to assess the applicability of cloud computing to their application areas.