What these companies do, the government would do in a much bigger way:
ChoicePoint (Wikipedia) -
ChoicePoint.com
Acxion (Wiki) -
Acxiom.com
Axciom - Yahoo Business Profile:
Acxiom Corporation Company Profile This company's handiwork shows up in our mailboxes. Acxiom is one of the world's leading providers of data and software used for direct marketing and customer relationship management (CRM). It collects and maintains a storehouse of consumer information covering nearly every household in the US and real estate records on more than 70 million properties that it offers to clients needing addresses, telephone numbers, and demographics for their direct mail and telemarketing efforts. Its CRM applications help companies manage customer data and can integrate that information into marketing systems. Established in 1969, Acxiom has operations in the US, Europe, and Australia.
Those are just a couple of the bigger companies - there are many more like them. The government would make them look like amateurs.