You can easily back up your bookmarks, too:
bookmarks
organise bookmarks
file
export
save as bookmarks2008 or whatever
and it’s saved an html file wherever you find handy. Nice to upload to a personal website if you don’t do social bookmarking.
Because it’s a great browser, and because i haven’t had a single glitch with bookmarks since way back at version 1.0.7 (i’m running version 3, beta 5 right now). I know that a very few people still occasionally open Firefox to find their bookmarks absent, but since the addition of the auto backup feature, losing them permanently is not an issue.
Also, for those who are interested, the Foxmarks extension allows you to synchronize your bookmarks among various computers, as well as keep a backup bookmark file on their server.