Ben Hammersley wrote a good post yesterday (below) about the importance of sharing, he used the analogy of a tree falling in the woods. However, even an unheard tree falling exaggerates the importance of posting online without sharing.
There are now over one billion websites and 30 trillion webpages on the Internet. Taking the tree analogy then; if a website is a tree, a webpage would be a leaf. In this scenario, publishing a new post would be not like a tree falling but a leaf growing. One leaf, on one tree, in a forest with a billion trees.
Put like this, if you don't share your content, it may as well have never been created.