Why Platform as a service?

I am currently in the early stages of my project which is an ERP application that I plan to sell to enterprise clients. I heard about the Force.com platform but I'm confused on what benefits will I gain if I use it and not develop my own. Can you please explain why should I use Forc开发者_StackOverflowe.com or any PaaS?

Regards,

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I think it has a simple answer. Building and operating such a platform is not an easy and trivial task in both business and technical perspective.

Of course, you may choose to develop your own platform but i think it would take a long time with much more money and efforts. I know it because I have been working for a company which is developing such a platform ( Viravis ).