The CEO of Aspera, a software company that specializes in data transfer for media, has published an article called How Can Hollywood Utilize the Cloud? She seems to suggest security is the biggest hurdle, without actually saying the word security:

Of course, the elephant in the room when it comes to data sharing in the cloud is reliable movement of data. Before entertainment organizations — or really any organization— exports their valuable data to the cloud, they need to be sure they can easily, quickly and reliably access it, from anywhere.

Reliable movement speaks to data integrity. Easy and quick, I would argue, are always at the top of requirement lists. The availability of information is an obvious requirement. No elephant there. Reliability also is likely to be found high on the list. All this is known to Aspera because their product is made for easy, quick and reliable data transfer.

Confidentiality, on the other hand, often gets left out of the discussion or postponed due to complicated and technical issues. Perhaps it is left out by the author in this instance for the same reasons. Thus, I would say the real elephant in the room for cloud data is the whole picture of security of data, which would be the classic pyramid of confidentiality, integrity and availability. If cloud gets this wrong, “reliable movement” means there will be massive data leaks/breaches like never before.