Just recently I have been reviewing several sites and storing the bookmarks as I went, I have been keeping them in a seperate review folder. I had noticed that XMarks was not running, when I had started it up, it flagged there was a problem with syncing and that it would carry out a download. While doing this it had not synced my recent bookmarks I had added on the machine, so once it had completed the download I managed to lose my recent bookmarks.
Lucky enough thanks to time machine I could get a copy of my bookmarks file just before I had lost them. The location you bookmarks are stored is
The tilda ~ means your home directory
If you don't use time machine you may want to grab a copy of this file so you don't lose your bookmarks.
I am always interested in feedback so feel free to add any comments, or you can mail me here, also if you would like to submit a quick tip with full credit and links back to your site then also feel free to contact me.