I just left this as a comment to a post on Software Testing Club. My newest comment, on Page 2 of the thread:
If you are talking about a transactional system – something like amazon.com – where you can measure the books that are successfully delivered and measure the failures, well, sure. Those transactions are roughly fungible. If we can assign a root cause to each failure, then aggregate the root causes and sort in excel, we can start doing problem-solving on the biggest problem first. That’s just basic six sigma, and I’d support six sigma for transactional systems.
The problem is we try to take systems that are /not/ transactional and make them such. A lot. We also use metrics to create smoke and mirrors.
The example above is a potential good use of metrics – and I’m remiss for not mentioning it earlier. In my experience, only a small percentage of software projects have metrics that can fit this paradigm.
Then again, there are a few thousand people who read this blog in a month, and none of them mentioned it either. So I suspect the percentage is relatively small, indeed.