When strategizing about who you're writing for, consider that audience's ability to help spread the word. Some readers will naturally be more or less active in evangelizing the work you do, but particular communities, topics, writing styles and content types regularly play better than others on the web. For example, great infographics that strike a chord (like this one), beautiful videos that tell a story (like this one) and remarkable collections of facts that challenge common assumptions (like this one) are all targeted at audiences likely to share (geeks with facial hair, those interested in weight loss and those with political thoughts about macroeconomics respectively).