When people search online, they leave a trail that remains stored on the central computers of firms such as Google, Yahoo and Microsoft. Analyzing what we're looking for on the Web can offer a remarkable understanding of our anxieties and enthusiasms. UK writer John Battelle wrote on his blog, "This can tell us extraordinary things about who we are and what we want as a culture." Google's experimental service Google Trends, for example, compares the numbers of people searching for different words and phrases from 2004 to the present. According to these graphs, sometimes people's interests are driven obviously by the latest news: when the Spice Girls, a pop group, announce a reunion, there's an immediate rush to find out more about them. Other results are strikingly seasonal: people go shopping online for coats in winter and sandals  in summer. The most fascinating possibility is that search data might help predict behavior. Perhaps we search for a political candidate's name when we are thinking about voting for him or her. This information could clearly be useful to a marketer - it's already how Google decides which ads to show on its search results pages - or to a political campaign manager. Marissa Mayer, a Google vice-president, argues that Google Trends correctly "predicted" George Bush's victory over John Kerry in the 2004 election. The graph clearly shows that Bush continued his lead over Kerry, in terms of search volumes, even when polls  suggested  _ . However, that's not always the case. For instance, the same approach predicted Hillary Clinton would beat Barack Obama in the race for the Democratic presidential nomination in 2008 turned out to be wrong in the end. On the whole, the author holds a view towards the search trail that   _
it is necessary to make rules about collecting the search trails people are in danger of letting out their personal information the search data is very useful to understand people in society search trails might cause a lot of disorder.