Many consumers have reservations about online behavioral targeting. By tracking users' online activities, advertisers are able to understand consumers quite well. Advertisers often use technology, such as web bugs and respawning cookies, to maximizing their abilities to track consumers.:60 According to a 2011 survey conducted by Harris Interactive, over half of Internet users had a negative impression of online behavioral advertising, and forty percent feared that their personally-identifiable information had been shared with advertisers without their consent. Consumers can be especially troubled by advertisers targeting them based on sensitive information, such as financial or health status. Furthermore, some advertisers attach the MAC address of users' devices to their 'demographic profiles' so they can be retargeted (regardless of the accuracy of the profile) even if the user clears their cookies and browsing history.
Affiliate marketing is commonly confused with referral marketing, as both forms of marketing use third parties to drive sales to the retailer. The two forms of marketing are differentiated, however, in how they drive sales, where affiliate marketing relies purely on financial motivations, while referral marketing relies more on trust and personal relationships.