From Declan McCullagh at CNet:
Your ISP as Net watchdog | CNET News.com:
"The U.S. Department of Justice is quietly shopping around the explosive idea of requiring Internet service providers to retain records of their customers' online activities.
Data retention rules could permit police to obtain records of e-mail chatter, Web browsing or chat-room activity months after Internet providers ordinarily would have deleted the logs--that is, if logs were ever kept in the first place. No U.S. law currently mandates that such logs be kept.
In theory, at least, data retention could permit successful criminal and terrorism prosecutions that otherwise would have failed because of insufficient evidence. But privacy worries and questions about the practicality of assembling massive databases of customer behavior have caused a similar proposal to stall in Europe and could engender stiff opposition domestically...."