You could fool a lot of work from advertising and marketing firms...
A new study by Jupiter Research found out that nearly 40 percent of Internet users delete cookies from their computers at least once a month. If this is true, it might be a big problem for marketers relying on cookies to track visitors and visitors behaviors'.
Quoted on ClickZ, Eric Petersen the analyst who wrote the report said: "Advertisers using lifetime value metrics need to reexamine how accurate that data is. The further away you get from the date the cookie was set, the less likely that the information is completely accurate."