Bitcoin isn't quite anonymous, as a variety of criminals have found out. Cash is anonymous: there is no unique identifier associated either with the transaction or the parties to the transaction.

Bitcoin on the other hand is, at best, pseudonymous. This is particularly problematic because it gives information about true identities when the owner of coins wants to spend it in any way on anything where bitcoin is not an accepted form of payment. Then, the "off ramp" becomes much more closely associated with the owner of the coins.

Heck, even in a world where on-ramps & off-ramps to bitcoin weren't necessary because everyone used bitcoin this would still be problematic: An address suspected of holding coins obtained through illegal enterprise pays a car dealership in bitcoins for a new car, and the authorities simply go to the dealership with a warrant and say "tells us everything you possibly can about that transaction and the people involved in the purchase & delivery of that vehicle".

And figuring out those addresses can come from finding another criminal address. By its whole design Bitcoin lets everyone see which wallets have transacted with each other.

Precisely. I'm not saying it's a bad thing, but it really doesn't mesh with the common bitcoin dogma of a virtual currency free of the ability of governments to interfere with it.

There's nothing stopping governments from shutting it down either. The US by itself could practically take it down alone (or any other crypto) by banning US banks from working with it, or from working with any non-US bank that that deals with bitcoin. No need for a 51% attack, no need to track electricity usage to locate potential miners, just a simple piece of legislation. Or even simpler, an executive order issuing the same ban, stating that bitcoin enables significant financial activity by terrorists & criminals.

I wasn't talking about bitcoin, I agree on all those points. I was talking about Chaum's digital cash

got it, I appreciate the clarification.