Web traffic may include click fraud
Just because a website receives a lot of hits doesn't mean a client is bombarded with eager customers. Some are paid to \"click\" on sites and type words into search engines-a mere $500 million problem or estimated 10% of advertisers' budget!
http://www.washingtonpost.com/wp-dyn/content/article/2006/10/21/AR2006102100936_pf.html
http://www.washingtonpost.com/wp-dyn/content/article/2006/10/21/AR2006102100936_pf.html