Your personal data's all over the Internet, and it's up for sale. Data mining is now big business, with some 4000 companies searching everything all of us do on line, looking for patterns and compiling lists for sale to marketers, financial institutions and perspective employers -- and don't forget about the NSA. It might be secretly mining even the data of its own corporate partners. If you've just applied for a warranty or googled somebody else's chronic disease, you could be on a list of bad credit risks or unsuitable employees. If the information is wrong, there's not much you can do to correct it, because it's secret and there's almost no regulation.