Search Engine Journal has a great article by guest writer Dave Davies about the guts, so to speak, of search engines and how they can affect search engine optimization.

Basically, this article is all about looking at the long-term. If you are doing something in your SEO efforts that won't work a month from now because search engines, being in a competitive business, have changed the way their spiders are looking at things, than perhaps you need to rethink whatever fantastic new tactic you've come up with. Davies writes:

"For a while keyword density spamming was all the rage among the less ethical SEOs as was building networks of websites to link together in order to boost link popularity. Neither of these tactics work today and why? They do not fit with the long-term goals of the search engine. Search engines, like humans, want to survive. If the results they provide are poor then the engine will die a slow but steady death and so they evolve.

When considering any tactic you must consider, does this fit with the long-term goals of the engine? Does this tactic in general serve to provide better results for the largest number of searches? If the answer is yes then the tactic is sound."

This is exactly what I've been talking about in my search engine optimization articles. You can't do anything, no matter how awesome you think it might be, without considering the long-term effects. Sure, you need to be flexible and move with the times, but don't go for the quick fix. This would include black hat SEO techniques, doorway pages, or spamming the engines.