"Unique Visitors" Must Die
Given growing bounce rates, we must stop using "unique visitors" as a metric for site success. Site tourists who leave a site immediately ratchet up the unique visitor count, but don't contribute long-term value.
On the contrary, bouncers should be considered a negative statistic: the site failed to engage them enough to entice even a second pageview.
To measure site success, you should count only loyal users who return repeatedly. Or, if your site is such that most people will visit only once, at least require that they exhibit a minimum amount of engagement before you count them as a positive statistic.
Chasing higher unique-visitor counts will undermine your long-term positioning because you'll design gimmicks rather than build features that bring people back and turn them into devotees and customers.
Read the rest at: Reduce Bounce Rates: Fight for the Second Click (Jakob Nielsen's Alertbox)