Clicky will only log a referrer for a visitor's landing page (the first page they view). This helps eliminate unwanted duplicates and ensures more accurate reporting.

The major reason we do this is because it is extremely common behavior for a visitor to click a link, click back, click it again, click back, click it again... you get the idea. We have no theories as to why people do this but because it is so common, many years ago we made this change. End result is that our referrer report is more accurate than most other services because we only count one referrer per visitor.