tedster - 5:23 am on Mar 8, 2012 (gmt 0)
It's that "correlation of many signals" factor that wipes out easy testing for cause-and-effect. You can have two sites that are apparently in the same situation (or at least very close.) A specific action seems to help one but has no effect for the other.
A big piece of this has causes in the area of taxonomies. Clearly, all kinds of signals will vary for different markets and different query terms.
Even something as simple as whether grammatically complete sentences matter, or as complex as the overall site history. The degree of variation that is allowed or expected is calculated regularly. If one slice of the web is a real gun fight, then all kinds of things may slip by that aren't going to pass muster in a quiet backwater.
It does seem that our time is better spent "chasing our customers" instead of chasing the algorithm. And really, for me that's a kind of relief. Search results are only a middle man - a mean to an end. Spending more time in direct work just feels right. But when something goes wrong with Google traffic, that's when the frustration kicks in.