The key concern is data privacy: users do not have control of or know where their data is being stored.
A universal set of standards and/or interfaces have not yet been defined, resulting in a significant risk of vendor lock-in.
The amount of control that the user has over the cloud environment varies greatly.
All access to the cloud is done via the internet, introducing latency into every communication between the user and the environment.
Many existing cloud infrastructures leverage commodity hardware that is known to fail unexpectedly.
Platform or Language Specificity
Some cloud environments provide support for specific platforms and languages only.