Are you still using cookies to track how many visitors you have and how often
those users return? If so, the numbers being used for determining the value of
your ad space may be overstated, way overstated. An article in the NYTimes - "The
Case of The Dissappearing Cookies" - cites a February Jupiter Research
report which found that 41 percent of male Internet users and 25 percent of
females manually deleted cookies at least once a week, adding that the figures
would be higher if they had included people who used anti-spyware programs to
delete cookies automatically.
In 2004, 18 percent of people who knew what cookies were said they deleted
them very frequently, according to a study by Revenue Science, which helps
advertisers find online audiences. A survey in December, 2005 reported a drop in
that figure, to 8 percent.