Readership is one of the most important things to consider when blogging. Knowing people are actually reading your blog is what encourages you to blog more; it's also important, however, to know why they are reading the blog. If, for example, half of your audience comes to your blog after reading your sports column, you don't want your blog to focus extensively on things that have absolutely nothing to do with sports.
I use StatCounter (www.statcounter.com) to keep track of my readers. This let's me see not only how many people are reading my blog, but also what search engines they are using, what blogs they're interested in, what state they live in, and even what kind of computer they're using.
StatCounter also gives me a way to thank people who have given me promotion. I've got as many as 3000+ visitors to my page because of a blogger I've never meant on the East Coast, who wrote a couple blogs about my book; he's now one of the first person to know whenever I publish a new article, and has been a very loyal supporter to anything I write.