The last of the cloud disadvantages/concerns:
Availability. The reliability component of availability is one of the selling points of cloud computing, but it’s also one of the problems. If you’re selling cloud computing, you point out that your systems are highly redundant and maintained by expert technicians. If you have a more jaundiced point of view, you note that cloud systems are much more complicated than the home or small business systems that they replace, and with that complexity comes opportunity for (mostly human) error. For an example of the level of complexity involved in some cloud services, read Amazon’s explanation of the April outage http://aws.amazon.com/message/65648/.
Even if the cloud proponents accepted that individual cloud computing services are less likely to become unavailable than their homegrown brethren, they would have to admit that a failure in a cloud computing cluster affects lots of users. The Amazon EC2 outage. Multiple Salesforce outages. Assorted Google outages going back more than two years. The Microsoft Azure and Sidekick outages. There are examples galore.
Even if your cloud supplier’s computers humming along like tops, if your Internet access is not working, neither is your cloud application. I have used many Internet service providers, and not one of them has anywhere near the reliability of my LAN. Ask yourself if your experience is similar.
Portability. In this context, portability means being able to move to another cloud service provider or to an in-house implementation of the service, taking your data with you. There are two components to this: gaining access to your cloud-stored data, and getting it into a form usable by your new implementation.
Consider cloud music storage. Can you download the music files that you paid for? What happens to the digital rights management associated with those files if you do so? Can you get the files into a format readily translatable to almost any music player? It’s easy to imagine scenarios where purchasing music from one cloud vendor essentially locks you into that vendor, unless you’re willing to repurchase your music from somebody else.