The other day, Laureen Hudson, a colleague made an interesting comparison that reminded me of Eric Peterson's discussion about the modes of a website in his book, Web Analytics Demystified.  We had been discussing Avinash Kaushik's blog post, Blog Metrics: Six Recommendations For Measuring Your Success

Laureen compared the number of site visitors to the number of RSS subscribers.  These could be called the potential subscriber & true subscriber segments.  Adding up the monthly unique visitors for the month and the subscribers for the month, gives the gross number of readers.  Then you can look at how much of the pie each segment comprises.  If your potential subscribers are over 50% of the pie, then you are in acquisition mode.   The higher the number, the stronger the acquisition mode.  The perfect mode is, of course, 50/50.  If subscriber numbers are increasing and the ratio remains the same, then you are growing at a great rate.  If the ratio is unbalanced, then you need to either publicize (<50 / >50) or work on subscription conversion (>50 / <50).

Laureen, you nailed a perfect marketing metric for blogs!