This happened in the popular tv show silicon valley but it's much more likely that your idea wouldn't result in something worth stealing. For example, I know of

This happened in the popular tv show silicon valley but it's much more likely that your idea wouldn't result in something worth stealing. For example, I know of a successful start-up that migrates cemetary data into a modern database and then sets up a site with it that allows users to view plots of land as well as buy them. Is Google going to hear about this and take over the funeral management business? It's extremely unlikely. Instead, what could happen is that the start-up one day grows very large and is acquired by a company, which then may have competition from Google or FB, if it turns out the market is so large that it's worth competing over. I would recommend that you pursue your ideas because generally you won't make the next Instagram. And even then, you'll probably be acquired before you have to compete with Google.