Time Machine backups are fantastic for reasonably technically aware folks, but it would still be too much for most "grandparents" to figure out how to dig out the bookmark files of Safari, Camino, Firefox, OmniWeb, Opera, Shiira, etc.

A lot of sync utilities provide some sort of option for automatically saving backup versions just before overwriting them with an Export operation.  This way a non-techie can easily Undo an unintended export.

Would something like this be possible for BookMacster?

(This would be especially good to have during beta-testing, too...)

Yes, BookMacster has some powers that Bookdog did not, and with power comes danger.  If you could recall the story, we'd really like to know how your bookmarks got toasted, so we could consider where more warnings or locks should be built in.

I've been burned myself a couple times by the Mirror-Save function (Export whenever the Bookmarkshelf document is saved), but it's always been because I'm constantly doing things that I've thought most normal people would not do, like deleting all bookmarks except one to isolate a problem.

To anyone else, if you've got a backup drive with Time Machine, all of your Safari, Camino, Firefox, OmniWeb, Opera and Shiira bookmarks are there in your ~/Library.  You don't need a special backup utility.  Of course, with web apps, Google Bookmarks and Yahoo/Delicious, they're not.  Once you overwrite your piece of the cloud, it's gone forever unless you have a very good buddy at Google or Yahoo! with root access to daily backups -- not bloody likely.