Cloud computing transforms the way Information Technology (IT) is consumed and managed, promising improved cost efficiencies, accelerated innovation, faster time-to-market, and the ability to scale applications on demand. According to Gartner, while the hype grew exponentially during 2008 and continued since, it is clear that there is a major shift towards the cloud computing model and that the benefits may be substantial. However, as the shape of the cloud computing is emerging and developing rapidly both conceptually and in reality, the legal/contractual, economic, service quality, interoperability, security and privacy issues still pose significant challenges. While the customers are excited by the opportunities to reduce the capital costs, and the chance to divest themselves of infrastructure management and focus on core competencies, and above all the agility offered by the on-demand provisioning of computing, there are issues and challenges which need to be addressed before a ubiquitous adoption may happen. First, in the cloud, the user may not have the kind of control over his/her data or the performance of his/her applications that he/she may need, or the ability to audit or change the processes and policies under which the user must work. Different parts of an application might be in different place in the cloud that can have impact on performance. Complying with regulations may be difficult especially when talking about cross-border issues – it should also be noted that regulations still need to be developed to take all aspects of cloud computing into account. Monitoring and maintenance is not as simple a task as compared to what it is for PCs sitting in the Intranet. Second, cloud customers may risk losing data by having them locked into proprietary formats and may lose control of data because the tools to see who is using them or who can view are not always provided. Data loss is thus a potentially real risk in specific deployments. Third, it may not be easy to tailor service-level agreements (SLAs) to the specific needs of a business. Compensation for downtime may be inadequate and SLAs are unlikely to cover concomitant damages. It is sensible to balance the cost of guaranteeing internal uptime against the advantages of opting for the cloud. Fourth, leveraging cost advantages may not be possible always. . Having little or no capital investment may actually have tax disadvantages. Finally, standards are immature and things change very rapidly in the cloud. Therefore, one cannot just move applications to the cloud and expect them to run. Finally, there are latency and performance issues. The Internet connection and network links may add to latency or limit bandwidth. In this talk, various service and deployment models of cloud computing will be first presented. In addition, some important aspects of cloud computing will be discussed, particularly focusing on the challenges in developing a regulatory framework for cloud computing, security and privacy issues, service quality and interoperability-related problems. Further, various standardization related activities in cloud computing undertaken in different Standard Development Organizations (SDOs) are also discussed. A top-level architecture of cloud computing depicting various cloud service delivery models will be presented, and various issues like service quality provenance, interoperability challenges, and critical security and privacy concerns are discussed with respect to the reference architecture. It will also discuss the future emerging trends in cloud computing.