Why ecash is traceable

[Hal]

Sorry, I don't have time to write much now.  The missing piece in my
description was the assumption that people would have to send received
cash to the bank non-anonymously.  However as Tim points out that can
be avoided in on line systems, and in that case Alice cannot actually
learn Bob's identity.  However as was also pointed out the cash can at
least be detected and invalidated so technically it is still traceable.
The protection of the payor is still not really as strong as that of
the payee.

I should also mention that when we discussed this earlier Jason Solinsky
suggested that transferrable cash systems also provide a means for Bob
to keep his identity secret.  The cash is still traceable in that the
bank can recognize it when it is finally deposited, but it may have
passed through many people's hands in the meantime and their identities
are not known.

Hal