Security is a very broad & complex topic. To create a secure application includes a lot of levels: The software, the infrastructure, the physical accessibility, and (maybe the most vulnerable part) the humans - and the policies and procedures associated.
Considering all aspects of privacy and security is a complex task, and best handled by experts of various fields. And as most of the companies are not in the security business, they should get experts for this.
Security and privacy of applications in the cloud are usually more secure -

its very true that u will get expert advice on security part, Questions asked by many organization (specially by Banks) is do they loos the privacy on their data... will the company providing the cloud will access it.
just to add on... in cloud there is a concept called Private cloud, public cloud and hybrid cloud. Private cloud will be dedicated to one particular organization; so their is no worry about any one having access on their private data.. and Public cloud is a shared cloud and more cheaper one. startups can go with public cloud and Big "O" can opt for a private cloud.

Web apps have to be open for public, thats their purpose - but security has to be managed carefully, as data should be well protected within the target group. This privacy / security can be best achieved by professional companies - hence: data often is MORE secure (not less), even in a PUBLIC cloud, as it is managed by professional security companies! -

i think - organization invest for their internal application, rather making their presence on web... i think you last post was referring to social media apps [i am not sure]...

the web site is less and less simply "the webpresence": more & more companies move more & more data & functionality to the web, accessible for their customers - I see that for example with Swiss banks: earlyer, everything was in the physical world, and the web was just advertisement - then, came eBanking, and now, more & more data is available on the web: real time credit card statements, share portfolio, load availability etc. etc -
Finally, most of the enterprise IT systems will be connected in one or the other way to 'the cloud' ...

cooperates can keep there apps on both for public and private space... depending on their requirement

The cloud is not primarily about sharing costs or using infrastructure in a more efficient way (even though this is a nice side-effect). The cloud is about FOCUSING on what a company does best: ITS BUSINESS, which is in most cases not about maintaining infrastructure -
The reason to go to cloud is quite the same, which made many of the largest companies in the world sell their real estate and rent it back. Of course they could 'afford' to buy their office space. But to manage real estate is their business and best done by professional real estate companies!

It's just that small businesses have a smaller workforce. For them, it is more important that they stick to what they do the best and not manage stuff which can be dealt-with by other experts. Price however is another important factor for SMEs to switch to the cloud.

It will definitely reduce the immense cost involved in setting up the IT infrastructure. Also the speed and flexibility business can have with the load shading concept of the cloud. Not just small organisations but the large enterprises will have virtually unlimited space, much more than their current capacity.