Martin McKeay has an article Write to learn, learn to progress where he talks about his history of blogging and how it has helped his career, this is a very good post with many good points. I've halfheartedly been blogging since 2004 and one thing I've realized is in order to be a good blogger and get "followers" you need to read other peoples blogs and contribute to ongoing "conversations".
I generally get half a dozen or so people who actually read what I'm writing currently and then I get a lot of "bot" traffic to my site. If I simply parrot what someone else says, I do get some more hits on that subject than some of the simple postings that I write, but that was someone else's idea, and the traffic that it generates is temporary, and I don't get much interaction from it, if any.
Now personally, I have several domain names, and I've tried to get author's to come and post on my sites, but I never really seeded the site enough to generate the interest. The traffic that site gets is more because of its name than anything, and I do cross-post there for items regarding information security.
For those who successfully blog, what is it that you feel makes your blog successful? And how do you measure that?