[Self-promotion warning] My blog that nobody read turned into a published book. An editor for a small publishing firm happened to come across my blog and thought that it might be good as a book. He contacted me and after about a year of work (more than I expected) I finished the book and got it published. It's not that popular, but I'm very happy with it.

My point is that you don't need a massive audience. If you can reach one person and make them laugh, or teach someone something new, or give someone hope when they really needed it, then your writing will be worth it.