Exactly. This idea that the entire Police force of an entire nation consists of the cop from the Simpsons is just asinine. People do realize that the FBI for example has a internet crimes division. They employ data analysts, statisticians, forensic accountants, computer experts, etc. FinCEN deals with ponzi schemes and other "investment" scams everday.
Since the logical jump from BTC to fiat seems insurmountable even among some bitcoin users lets replace BTC with Gold. Imagine Pirate ran a Ponzi where "investors" were encouraged to mail in gold and would be credited the amount of grams deposited and interested owed. They could get their weekly dividends mailed out to them and even request a withdraw of all gold owed and be sent other investors deposits. Now Gold isn't money but it does have value. Police do investigate theft of things which have value.
The idea that Bitcoins have no value and therefore no crime has occured is just silly. No judge is going to rule that way. Sex for Bitcoins = legal loophole. Bitcoins have no value therefore the prostitute isn't engaging in prostitution. Ransom for bitcoins = not a randsom just free speech. Bitcoins have no value under the law remember.