You'll find different answers to this question over internet as there is no single best answer. But working closely with someone at AWS (Amazon Web Services i.e. Cloud Computing), I believe there are following most important points:
1. Scalability: Cloud computing gives great benefit of not worrying about the data size that you might need in future. e.g. Facebook cannot exactly predict how much data it'll need after 2 years. As users keep growing, it might need any terrabytes of data. They need to pre plan that and risks are: a) Overestimation: you might end up buying lot of additional systems/data storage and never need it(unnecessary expense) b.) Underestimation: You might end up buying lot less than you actually need (causing not enough storage when user base grows.) Cloud computing removes that burden from you as you might request increased data storage systems anytime. Hence you can keep requesting additional infrastructure as you need.
2. Focusing on business: You can focus on core business instead of hiring experts to maintain data centers and buying those data centers. A common businessman is not tech savvy and using your own data centers can pose serious issues. Cloud computing allows business owners to focus on main business and not worry about something which they can kind of "outsource".
1. Data Security: One of the biggest challenge is that your data will reside on third party servers/data centers. No one would like to expose their firm's confidential data to third party so still lot of firms don't buy the idea of Cloud computing. However, in my opinion there are trusted services like Amazon which can be used. e.g. NASA keeps its data in Amazon data centers so it is reliable.
Hope that answer your query.
Content will be erased after question is completed.