Predictive marketing is used by websites such as Amazon and advertising publishers such as Google and Facebook.
While direct marketing (displaying the same promotional material to all consumers) and content-relevant ads (showing promotional material related to the content of an article) are both personal advertisements, they are independent of the particular consumer.
The statistical nature of predictive buying means it will never match perfectly every time - some advertising space will be taken up with adverts that do not work.
Critics, such as Cory Doctorow, have pointed out that this mismatch creates a sort of arms race between marketing firms - who try and collect more and more data to further improve their predictions - and consumers, who over time learn to ignore or become desensitized to adverts.
[3] For the business owner, the consequences of this arms race are that most of the money that is spent on predictive marketing will be wasted because, like all advertisements, they will be ignored.