Like many phrases, 'long tail keywords' can mean different things in different contexts. There is the long tail of all keywords, the long tail within a market or a niche and the long tail within a 'keyword niche'. A keyword niche being all keywords containing a single seed keyword, eg, 'red socks'.

For me, a keyword niche is a 'gem' if it delivers good response and I can get visits for it. The amount of investment in SEO it gets depends on its size - it might get 5 minutes work or a year long campaign. You can priortise by ROI regardless of size.

But until I have proven I can get traffic and response from a keyword niche it's just a theory. Once I have that proof I can exploit that keyword niches whole body including its own long tail.

IMO, long-tail doesn't mean different things in different contexts.

As it relates to keyword phrases, it always means those phrases which individually are not searched upon very often, but which in aggregate can add up to a good amount of highly targeted website traffic.

I suppose one could argue how to define "very often" as it could be once a day, once a week, once a month, or once a lifetime, as I mentioned in the original article. But other than that, the definition is clear.

If you take your fixed definition and apply to the different situations I refer to then it stands up. That's because you're using general phrases like 'not searched for very often' and 'good amount'. These phrases only have a specific meaning when used in a context. I give three different contexts that would give them different meanings.

Eg, when looking at a large sample of searches as Bil Tanner did in his famous long tail study, 'not searched for very often' and a 'good amount' might mean thousands and millions of searches.

And if I have site selling socks then the numbers would be smaller.

The concept and principles remain the same so in that sense the meaning of 'long tail keywords' is fixed (your point I think). But the numbers are different and so it is different (my point). And that leads us to a practical point - the concept is useful at different scales so long as your SEO tactics adjust accordingly.

"If you want to capitalize on the long tail, look beyond rabid link grubbing and learn to optimize your pages. Optimized, relevant content is what gets long tail traction."

That hit it right on the money. My site rankingclimber.com is ranked on page one of Google for the keyword phrase: "getting ranked". My site doesn't have nearly as many back links as the other pages on page one of Google, but what sets my site apart is that my content is dead on with the search phrase. My bounce rate is close to 15%, which in my opinion is very low. People stay on the site and keep reading how to get ranked on google. Content is king. I truly believe that. But sometimes with a dead on link building campaign, you can trump content.