Cloud computing is emerging fastly and no doubt it is the next generation technology where humans will be using anywhere and anytime. In this internet world cloud computing is raising high by providing everything incense the required resources, applications, software, hardware, computing power to computing infrastructure, business process to control collaboration. Today clouds with virtualization are transforming IT. Apart of its popularity it has some concerns which are becoming huddles for its wider adoption. In this paper a study has been made on virtualization concerns.