Why is this important? Backlinks play a big part in how search engines (especially Google) rank your blog. The logic is that your site must have some decent content in order to make someone post the link and then, in turn, make someone else want to click on the link. The internet is not perfect. But the backlinks work better than just judging a site by the number of clicks that it has (easily faked).
This is partially why it takes so long for a blog to get steady traffic because you are literally just waiting for a healthy number of backlinks. Consistently posting high quality, engaging content is the best way to ensure backlinks.
Basically, you want one of your blogs to become one of those email forwards that everyone passes around. This doesn't mean spam people. It means you should make content that people would want to share with others.