Humans have a tendency to think linearly, even if the nature around us is mainly nonlinear. Predicting linearly, can be compared to driving by looking out the back window.
Jacop Nielsen has a recent article about website traffic analysis and linear thinking.
With a nonlinear (logaritmic) transformation of the data, he draws this conclusion:
"It's now clear that we have a drooping tail: the site simply doesn't have enough content to supply the predicted demand at the low end.
Without this fancy log-log plot, we would have never seen the site's potential for increasing traffic by adding large amounts of low-volume content. I'm amazed at how often articles analyzing Web traffic or "long tail"-type businesses use linear plots that fail to show what's really going on".
And if you use a spreadsheet like Excel for your traffic analysis, a loglinear analysis is done by simply double-clicking each axis, choosing the Scale tab in the resulting Format Axis dialog box, and checking the box for Logarithmic scale.