Seth Godin had a great post about common metrics mistakes.  Here’s his list of the common stuff we measure, followed by the actual stuff we’re trying to figure out.

Good grades in school (the ability to solve problems in life)

Lots of raw traffic to your blog (conversations among prospects who become fans or customers)

Burning calories (feeling better and looking good)

Clickthrough rate on ads (conversion rate to customers)

High salary (long-term happiness)

Class rank (actually learning something)

Number of stock options (future prospects of your employer)

This quarter’s commission (reputation in the industry)

Technorati rank (number of RSS subscribers)

He’s right on the money – it’s the forest for the trees thing – at somepoint or another all of us will forget the actual goal and start managing towards the metric. It’s kind of like the difference between having sex and having your buddy tell you about the sex he had – if the telling of the story is better, you’re doing something really wrong.