The GM often needs to get a character sheet from a player. It would be nice for the player to be able to send the character sheet to the GM from within ajaximrpg.
As I imagine it, the document tree would have a shared area and a private area. Documents added to the shared area would automatically pushed to all the other users in the room; if others added items, those changes would be received by the user. The private area would remain private to the user only. I would imagine it as a tree control with all folders being public except a single folder named "Private".
A bookmark system (a.k.a. URL links) seems like a good way to go. The HTML pages that are bookmarked could do their own synchronization from within the HTML page to synchronize the content.