This one is for all of the techies out there. I have a somewhat love hate relationship with SEO forecasts. Partly because most agency forecasts are ludicrous, and partly because forecasting is so complex, it interests me. This post is a good introduction to time series forecasting in R, and how to use exponential smoothing.
We've all seen plateauing performance in SEO. It hurts. And as Kevin acknowledges in this article, it's seldom as a result of one thing. There are some core issues that cause organic traffic to plateau and he has listed most of them in his most recent post.