Over 95% of blogs are abandoned after just a few posts.
I made up that statistic on the fly, so allow me to be slightly less lazy. A study by Technorati claims that of the 133 million blogs they tracked since 2002, only 1.5 million saw activity in the week they surveyed (in June 2008). This is a measly one percent. If we're more generous and include the blogs that saw activity in the last three months of the survey (to allow for people who update less frequently than once a week), the number climbs to 7.4 million, which is still only 5.6%. The total number of posts such blogs see was not recorded, so my made-up number isn't exactly corroborated, but it does strengthen my confidence.
You need a sense of discipline and purpose to keep blogging; after a few posts of nobody commenting (except perhaps the people you quasi-forced to), the "what was I doing this for again" feeling sets in and it becomes harder to motivate yourself. Yet the best blogs don't consciously set out for an audience to cater to on day 1, and even the ones that do know not to actually expect such an audience to be present on day 1. You must have the will to write, and have it so strongly that all the excuses you could provide for not maintaining the blog fade away. If your blog is of any interest to anyone, it will pick up an audience automatically.
Every so often I have a "this would be nice for my blog" moment, but then I consider the time and effort required to type up a post, sigh, and give up. All things considered, however, this is nonsense. I have plenty of time to make a post — perhaps not immediately as I think of it, but certainly some time afterwards. Perfectionism plays a role here, too — if you want every post to be a perfect little shining gem of awesomeness, obviously it will take you much longer to post than if you just stop when it's good enough. It's just a blog post, not a marble statue!
With that in mind, I've resolved to better my ways, or "reevaluate my priorities", as they say in middle management, and decided that 1) I can post with some frequency greater than once per month and 2) I don't really care who reads this blog, if anyone; I write these things down because I like writing them down, and if they happen to be interesting or helpful that's just an added bonus.
Now the "frequency greater than once per month" thing is still a cover-my-ass bit, of course — if I were really committed I'd promise to type up a post once a week. But I find that such promises are far too easy to break (who's going to hold you to them?) and when you do break them, it's just an incentive to let it slide completely ("well I didn't post last week so I don't really have to do it this week either"). So, for now, let me just limit it to "it ain't dead yet, baby".