Here's a thought provoking article about the problems of large-scale data mining by governments. It's written by a person living in the UK.

"Data-mining is complicated, and the more data you are mining, the more false positives your software will throw up. If you act upon a false positive for a motoring offence, it's an inconvenience for the motorist, but for an alleged case of child abuse, it can rip the family apart and ruin the child's life."

"Furthermore, gathering large amounts of data is inherently dangerous. Whatever information governments find interesting will also draw the attention of criminals. Databases can be hard to keep secure, and it's not necessarily hackers that we should be worried about, but unauthorised access by employees of the agencies that use these databases. Equally, the more data you have, the more difficult it is to maintain accuracy. In 2000, an audit of the Police National Computer found that 86% of records contained errors, 85% of those errors were serious, and some were libellous."

"Technology can be a very powerful tool, but what it can't do is replace real human beings or traditional investigative work. Designed badly or used poorly, databases are the technological equivalent of fools gold."