Brian Carter of Fuel Interactive raises an interesting point about the effectiveness of keywords in the long tail of pay per click advertising. It has long (in Internet time) been thought that advertising on a huge portfolio of search terms will generate better returns because you'll get a trickle of traffic from thousands and thousands of terms at low cost per click AND the traffic will convert at a higher rate for a double gain in returns.

However, Carter explains that this isn't necessarily the case:

The Problem with Long Tail Keywords

But the dirty little secret of PPC is that 95% of your conversions come from 5% of your keywords.

Really.

The others keywords either

* Don't perform (100 clicks and no conversions), or
* The clicks roll in so slowly that you won't have the statistical confidence to delete them until the year 2112 (yay, Rush!).

As I said, interesting points.

While 95% of conversions may come from a small sub-set of a keyword portfolio, that doesn't necessarily mean that the rest of the portfolio is underperforming. The rest of the terms may not deliver as many conversions, but that's not really a measure of performance. Return on investment would be a better measure.

But more importantly, I think the biggest concept that could be misunderstood here is what I'll call "micro-short-tails." By that, I mean terms that get relatively few searches, but are still clearly short-tail terms when looked at on a page by page basis. For example a retail site could have thousands of products in inventory - some of which are relatively obscure. On a page by page basis, it's pretty clear that product-names and product-IDs would be considered short-tail terms while on a site-wide basis they would look more like long-tail terms.

In many cases, patterns of "micro-short-tail" terms can be generated and properly targeted to truly relevant pages.

Is this long tail or short tail? In my opinion, it's all relative.

I think Brian and I would agree that measuring what's working and building upon successes is the key to running great pay per click campaigns regardless of how different strategies are defined.