"Well, isn't that obvious?" How often have I heard this said? Usually by someone for whom it was not at all obvious (based on their actions) just a millisecond before they uttered these words.
At the risk of offending some (though believe me, not intentionally . . . this is a good-hearted blog), I'd like to quote* something attributed to Jennifer Laycock, Editor of the Search Engine Guide, from her presentation at SES - San Jose ("Big Ideas for Small Sites & Small Budgets" - moderated by one of our favorite people, Anne Kennedy):
"Number one rule of PPC…it’s not about buying clicks, it’s about buying customers! Just because it is a higher CPC does not mean it is converting better. You have to track actionable item interaction by visitors. If you do not know what converts best, you are wasting time. PPC without metrics is like launching tv, yellow pages, and direct mail on the same day without tracking them."
In other words, it's all about the conversion! This cannot be said enough.