That depends on a lot of factors. Do you really, honestly think you can make it better than what already exists? What is in it for your customers, can you make

That depends on a lot of factors. Do you really, honestly think you can make it better than what already exists? What is in it for your customers, can you make their lives better? Does your (financial) life depend on it or do you do it as a side project for the fun of it (1)? Can you refine your idea with real user feedback or are you on your own? etc... (1) I develop a community climbing blog and a web framework as side projects, just for fun. The rules change when you do things just for fun - see also my blog post "Why re-invent the wheel" http://davidtanzer.net/node/81 http://davidtanzer.net/node/81