As I've mentioned before, I'm having a lot of work done to my home. One of the jobs is to have the landscape contractors put in underground drainage in my backyard to help the water drain better. So, a few days ago, they hauled in a ton of dirt to level the ground. Because the three that showed up to do this phase of the job were Larry, Curly, and Moe, I ended up with a mountain of dirt that did a great job of plugging up the back yard, with no chance for water to be able to flow out. Of course, the next day it rained for hours, and I now have a lovely lake behind my house.
They are out there right now feverishly digging ditches to get the water to move on out.
Rather than cry, I sat down here at my computer to vent a little, and decided to make yet another comparison to SEO. Moral of the story: When optimizing a site, don't plug it up! Think about the possible effects your changes may have on the rankings. They may not be what you intended. Plan ahead for that rainy day (algo changes?), and don't leave a pile of dirt (robots.txt screwups?) that may block the water from flowing (search engine crawlability?).
Ok, enough stupid analogies for today.