Revisiting my original post:
http://archives.postgresql.org/pgsql-hackers/2010-11/msg00318.php
The "Web SQL" spec is still in its abandoned state.
Mozilla has stated that they do not want to support the API,
though they do allow extensions to send calls to sqlite directly.
Many posters responding to my OP, noted that exposing "SQL" directly,
even with permissions, is not something they're comfortable with.
IndexedDB has gained acceptance across Mozilla, WebKit and Microsoft.
SQL is not exposed directly. It's a simple system.
IndexedDB is currently implemented in WebKit and Mozilla browsers on
using the SQLite library. MS recently implemented a .Net prototype.
I'm going to compile libpq as a browser extension to prototype indexedb
with postgres, then work on patches to WebKit to develop a libpq flag
[default: false] for webkit build scripts.
I will post back when I've got something to demonstrate (hoping to get
to it in a few months).
-Charles