Should I worry about my product/service being copied by a bigger company?
That a concept/product/service can get copied is a real risk. You cannot wish it away by assuming that your passion and enthusiasm will help you win the war. You have to manage that risk well.
There are two ways of dealing with the risk of getting copied or someone else doing something similar.
If your idea patentable, go ahead and protect it. As you will know, many large companies create a forest of patents around their core product patent. Hence, when you do a patent search you will also know if your concept is infringing on someone else’s patent. And if it is not, go ahead and protect yourself by patenting your product.
2) Build a value proposition that helps you win
As a startup, you have several advantages over a larger company. The ability to be nimble and respond quicker. The ability to devote much more attention to that client than a larger company possible can (the larger company can thrown more professionals at the client… but that cannot match the passion & commitment of a founder).
Other way to differentiate, and thereby create a preference even if there is competition, are pricing, brand personality, service levels, business models, etc.
Remember, in most markets, especially if the opportunity is large, there are likely to be many others who will take a shot at that market.
Go ahead. Be confident. But not over confident. Plan well. Plan thoroughly. Implement well. Be patient. Be creative (in everything expect in legal and accounting). Go win.