Things like cookie inspection allow a data miner to get a list of known customers of a company. I can tell you every RackSpace Customer, Every Amazon Shopper,

Things like cookie inspection allow a data miner to get a list of known customers of a company. I can tell you every RackSpace Customer, Every Amazon Shopper, Every FaceBook User. If you have seen those ads on FB that are for something you just searched on Amazon, or that want to sell you hosting for a place you already have hosting with you know what I mean. If you have enough data about the factors that are common of people with a disease, and then compare that with percentage of people known to have that disease from a set. If 10% of Company's American clients have Disease X, and Disease X requires you live in a cold climate to be diagnosed ( Raynaud's for example ) then you can exclude the people who live in a warm climate. Now if you want to target people with Raynauds and you know 80% of the clients live in California,Texas, And Nevada. You know that 50% of the remaining clients have Raynaud's. This is of course a contrived example, and uses much less data than would be used by a Data Miner. For the people saying "no there are formula's we can prevent this from happening" yeah you know who made those formula's? The People who make money selling data. And thos formulas are to keep you from thinking it is dangerous.