Implementation Of cloud Computing

For instance, if you want just any cloud then botnet malware will sort you out.

But if you want to make a cloud app, then you have to do the whole servers and clients thing.

If you want to implement an existing cloud app then just ask the marketeers of various vendors, they'll be happy to give you an earfull.

compatibile application.

You have to design for it, it's a different platform.

You need separation of concerns, encapsulation and modularity to be inherrent to the design, and as close to rigidly applied to the implementation as you can get. Otherwise cloud benefits will start minimal and get smaller.
Never mind all the concerns surrounding using a third party to host it, or doing it yourself...