An interesting study reported at New York Times:
But neither of these is the most valuable kind of Web site visitor. That honor goes to the people who arrive at a site by typing its Web address directly into their browsers or clicking on a bookmark. Such visitors, who tend to be repeat customers, linger the longest, spend the most money, and are the most likely to â€œconvertâ€ to buyers, doing so on 3.3 percent of their visits. On average, their visits are worth $5.69 apiece.