Why didn't you patent it? I often think when I see the tag no one will steal your idea, only applies if you're idea isn't worth stealing - 'I'm gonna sell some stuff' isn't really an idea, it's just business, and so how you do your business matters - i.e. execution.

However if you come up with a truly new idea - a better compression algorithm for example - then the idea matters and execution matter as well. It's just truly new ideas are rare, and so the 'execution matters' mantra continues, because most new businesses aren't new ideas just different packaging.