Eurydice - 3:41 pm on Apr 4, 2010 (gmt 0)
Although longtail terms are only a fraction of terms in the head, the majority of searches are in the longtail.
1) The statement is not true. Generally, a handful of KWs account for 90% of traffic. Of 1,000 KWs, maybe 15-25 bring in the traffic. And often, one or two KWs produce about half of that traffic.
2) The statement is also not useful. Let's assume the statement is correct ("the majority of traffic is in the long tail"). But that traffic comes from 45,000 different keywords, and each one gets only a few clicks. With such low numbers, there is no statistically meaningful data. A keyword got five clicks and three conversions. So what? That is too little to draw any conclusions.
3) The statement also damages your Adwords account. If you add 45,000 KWs (fluffy pink credit card, furry green debit card, etc.), they'll not have keyword relevance, so your keyword quality score (shown in Adwords Editor) will be low. This will lower your cumulative quality score, which lowers your overall impression share and increases your cost-per-click (you get punished for a bad cumulative quality score).
PayMePerClick is correct: An ad with a very low traffic KW won't even show.
Listen to my cat. The long tail is skinny. Just bone. The good stuff is in the fat body.