Re: How many ?
"In fact all you cited can be called in one word - webserver. So "industry" is just one."
webserver an industry? Surely it's a technology? And most of the industries I highlighted need more than just webserver technology - databases (structured and nosql) to hold the data, middleware to handle the business logic and integration with other services (payment processing, order fulfilment, media encoding), analytics for, well, analytics, user management systems to handle AAA, etc. All of these need to scale (to different proportions) in response to changing demand on the systems.
If you disregard the advertising and PR hype around "cloud", the concept of technology services that scale up and down rapidly and on demand are logically sound (and have been used in more manual ways, such as recruiting seasonal workers, for decades). The problems organisations face relate to the lack of capability of a "traditional" application stack to easily make use of this type of flexibility, together with the business analysis to understand when there are benefits of using cloud v in-house technology. For these reasons, cloud delivery of some services are often (much) more expensive than alternatives, as the article highlights.
Going forward, more enterprise apps will be built with a cloud delivery model in mind. In the same way that it's possible to generate your own electricity, and historically you had to build your own generators, nowadays most people buy power from a utility provider. Similarly, the time will come when it is both easier *and* cheaper to buy commodity IT services from a utility provider. In-house delivery of technology will be done for edge-cases only.
This move to commoditisation will be competitive and brutal, and be based primarily on scale; in the same way that there are only a small number of national electricity providers in the UK, a similar thing will happen (and is happening) to cloud providers as the industry matures. Take Rackspace, which have already dropped out of the cloud price wars. I would put a bet that in 5-10 years time their main focus (and revenue) will be on their managed services, rather than their infrastructure.
Disclosure: I work for an SME managed services provider, that runs its own cloud infrastructure - but there will come a time in the future when it makes more sense, technically and commercially, to use commodity IaaS providers (plural), managed properly, to deliver some of these services.