Why, because bills have serial numbers? Presuming that ecash "units" will also have serial numbers, that would mean getting caught with a flagged unit in your p

Why, because bills have serial numbers? Presuming that ecash "units" will also have serial numbers, that would mean getting caught with a flagged unit in your possession could land you in hot water (just like getting caught with marked bills). But without a public ledger, ecash still wouldn't be amenable to forensic accounting in the way bitcoin has proven itself to be.