In the beginning, my site was sharing webspace with someone else, and I wanted to tread lightly. Being searchable means a lot more visitors, and I wasn't confident that my site could handle it if I got listed somewhere. In retrospect, I'm pretty sure it wouldn't have. I've improved performance quite a bit since then, but I still don't think I could handle a slashdotting (even with /. in its decline).
Also, I like being a recluse. I don't always say nice things, and if those things are easy to find, people may get the wrong idea about me. This is, of course, unnecessarily paranoid. Furthermore, it's opposed to my ideals of openness and Constructive Bastardism. I wrote these things because that's who I am, and I shouldn't hide it.
More recently, I've been getting spambots, and being un-indexed provides a significant disincentive to spammers because their links will go un-noticed by search engines. Still, they come around occasionally, and some comment spam is designed to fool humans, not computers.
So I've decided to open things up by removing the robots.txt entry for /blog/, and damn the torpedoes.
To this end, I've hardened the comment entry system. Most HTML is still allowed, but attributes are restricted to prevent javascript and CSS shenanigans, and people posting flash or java applets will be... punished. If spam becomes a problem, expect the addition of some kind of captcha. This, of course, only applies to guests. I can still do whatever the hell I want. :-P
Hello, World. :)