writes "Computerworld reports that in testimony before Congress the US Department of Justice renewed its call for legislation mandating Internet Service Providers (ISP) retain customer usage data for up to two years because law enforcement authorities are coming up empty-handed in their efforts to go after online predators and other criminals because of the unavailability of data relating to their online activities. 'There is no doubt among public safety officials that the gaps between providers' retention policies and law enforcement agencies' needs, can be extremely harmful to the agencies' investigations,' says Jason Weinstein, deputy assistant attorney general at the Justice Department, adding that data retention is crucial to fighting Internet crimes (PDF), especially online child pornography. Weinstein admits that a data retention policy raises valid privacy concerns however, saying such concerns need to be addressed and balanced against the need for law enforcement to have access to the data. 'Denying law enforcement that evidence prevents law enforcement from identifying those who victimize others online,' concludes Weinstein."
Think about how much evidence is denied to law enforcement by envelopes, opaque concrete, and criminals' failure to shout.