data storage: structured text files are good... you should be able to
dump text in and out (e.g. from a texteditor, to a blogging tool)
relatively seamlessly.

persistence: ideally, should save after each edit. doing this in the
browser is non-trivial (how does JS handle filesystem stuff? security
restrictions?). What about webDAV? XML-Http? If all else fails, manual
save should be possible. I would LOVE to be able to stick the whole
thing on a usb thumb drive and run it from there, on multiple
platforms.

architecture: max cross-platform compatibility appears to be a
priority... The way I see it, it should be able to run locally, and
sync with a backend for backup, or for other functionality
(notifications/reminders, export to wiki or other db, hooks to
whatever). I plan to study the gmail, and google suggest (livesearch)
architectures for clues. But DHTML + XML/HTTP + robust server backend
seems like a good place to start.

what kinds of data nodes are we talking about, by the way? full-fledged
wiki content? todos? something in between?

more thinking out loud....
--Josh (the other one)

PS: the google groups web interface sucks... what's a better way to
read individual threads?