So, I'm assuming that your goal is to get a lot of users, and gain some market traction, demonstrating both that a market exists, and that people want to pay for this functionality.

So my point is, now that you are successful (to VC levels of success) then you become visible to others - like (but not necessarily limited to) AWS. At that point what stops them just using the code to offer the same service?

Obviously there is room for lots of small companies, providing useful services that customers pay for. If you plan to be small, and niche, then you can make a very successful business. But that business is perhaps better aligned with boot-strapping rather than have VC-style investors.