“Cash became the crime. The government figured out that drug sales weren’t done on Visa or MasterCard, but in currency. Evil currency. So they criminalized cash. But that still wasn’t enough to feed the hunger of the government and starve the drug kingpins, so then the ‘instrumentalities of the crime’ was conceived. If you drove to a drug deal, the car was an instrumentality. If the drug deal happened in a house, the house was the instrumentality. And even if there was no drug deal at all, it was all an instrumentality or substituted proceeds. Take the profit out of crime. This became as important, if not more so, than proving the existence of a crime at all. And it was so much easier.”
http://blog.simplejustice.us/2014/09/20/the-forfeiture-curmudgeons/