Thanks for your comments. I entirely agree with almost everything you wrote, except that you must see that the simple example you provided, though a single case, does not back up the thesis of the post. It is very important for people to understand and be skeptical of a overly simplified analog approach (we see this a lot in the field); I understand that is the purpose of the post. However, even a simple method like the one you designed, if done on the entire data set, could be a useful tool with a quantified estimate of forecast skill. As you said, it seems it shouldn't be as good as a multiple linear regression, though.