Good article in The New York Times about weblining:

Stereotyping is alive and well in data aggregation. Your application for credit could be declined not on the basis of your own finances or credit history, but on the basis of aggregate data — what other people whose likes and dislikes are similar to yours have done. If guitar players or divorcing couples are more likely to renege on their credit-card bills, then the fact that you’ve looked at guitar ads or sent an e-mail to a divorce lawyer might cause a data aggregator to classify you as less credit-worthy. When an Atlanta man returned from his honeymoon, he found that his credit limit had been lowered to $3,800 from $10,800. The switch was not based on anything he had done but on aggregate data. A letter from the company told him, “Other customers who have used their card at establishments where you recently shopped have a poor repayment history with American Express.” …   In the 1970s, a professor of communication studies at Northwestern University named John McKnight popularized the term “redlining” to describe the failure of banks, insurers and other institutions to offer their services to inner city neighborhoods. The term came from the practice of bank officials who drew a red line on a map to indicate where they wouldn’t invest. But use of the term expanded to cover a wide array of racially discriminatory practices, such as not offering home loans to African-Americans, even those who were wealthy or middle class.   Now the map used in redlining is not a geographic map, but the map of your travels across the Web. The term Weblining describes the practice of denying people opportunities based on their digital selves. You might be refused health insurance based on a Google search you did about a medical condition. You might be shown a credit card with a lower credit limit, not because of your credit history, but because of your race, sex or ZIP code or the types of Web sites you visit.

Redlining is illegal. Seems to me that weblining ought to be illegal as well.