e$ as "travellers check?

[Eric Hughes]

   But someone a long time ago brought up traveller's checks, and the
   similarity between them and ecash. [...]  You pay some money to
   American Express, you get a note issued by them, you give it to a
   merchant, he redeems in with AE for money. [etc...]

   I dont' know much about economics, but as far as I can tell this
   seems a pretty solid analogy.

What you have described is a financial model for digital cash, which
is only part of a complete model.  The financial model is, as you
point out, pretty easy.  You buy an instrument and then use it in lieu
of a more direct transfer.  The privacy to counterparty comes about
because the issuer's name is on the instrument, not yours; the issuer
is a proxy for identity.

   It's clearly not _illegal_ to issue
   travellers checks, 

No, but in certain places where they are used in lieu of greenbacks,
aka Federal Reserve Banknotes, it _is_ illegal to use them without
certain reporting requirements.  (Duncan can elaborate, as he's much
more up on the details here.)  Complicity in failure to report can
also be criminal.  And an issuer that sets up a system to thwart
reporting requirements could easily be considered _prima facie_
evidence of conspiracy to evade reporting.

When the government doesn't want anonymity, expect that it will be
difficult to create.

Eric