It happens all the time. The most prominent case was/is American Express mining spending patterns to characterize users into various categories. Here's a slight

It happens all the time. The most prominent case was/is American Express mining spending patterns to characterize users into various categories. Here's a slightly dated NYT article on the issue: http://www.nytimes.com/2009/01/31/your-money/credit-and-debit-cards/31money.html?_r=1&ref=business http://www.nytimes.com/2009/01/31/your-money/credit-and-debi...