TheGoogleCache had a great post today about site re-evaluations and penalties. It’s interesting to note, and I agree, that just because you lose ground in the search engines it doesn’t mean your site is being penalized. Specifically, here’s one point I’d like to highlight:
Your site may have lost a handful of high-quality links. Websites disappear (especially older ones which may have been providing you a lot of PageRank pass-thru), other sites begin to implement No-Follow, blogs, comments and press-releases get auto-pruned. Because the quality of the link matters so much, you could track your back links and believe your site to be growing in Link Popularity, but actually be losing your most important links.
This re-pruning is exactly why you should not rest on your link building laurels. Just because you built 1,000 links in the last six months and those links seem to be helping your rankings, that doesn’t mean that they will benefit you two years from now. Old link partners fade away and the search engines change their algorithms. It is highly likely that you will have some pages lose PageRank and even search engine rankings at some point. That’s why you need to keep performing link building tasks over time. Because the more new links you add today the more you will benefit the next time Google decides to update its algorithms or completely re-evaluate your site. Old link partners will die, let the new ones rise.