[grandalf]

It would seem that this makes it significantly easier to stay under the radar -- simply set up your credit cards to suggest a very normal life and then use cash for any illicit activities.

And, if a group of people (such as a terrorist cell) wanted to, it would be easy to deliberately create a paper trail to mislead authorities.

[jrockway]

You get promoted based on how many cases you solve, not how many difficult cases you solve. If you are smarter than the average criminal, you probably stand a less-than-average chance of being caught.

[sielskr]

because the authorities have no control over the supply of cash, would never try to outlaw cash, or never require banks to report the withdrawal or deposit of cash.

[grandalf]

At the levels necessary to do terrorist acts, cash is essentially unmonitored.