Using Sync shouldn't result in bookmarks getting lost, but sometimes it may take Sync a day or two after an additional device is connected to Sync for the full synchronization to take hold. How long it takes depends upon the amount data Sync has to deal with and how busy the Sync server is when an additional device is added to the account. Sync is fast, but sometimes it shifts into what I would call a "bits & spurts" mode - at least based upon my experiences with Sync. ------------------ Also, if you do any massive rearrangement of your bookmarks or go to reorganize them, Disconnect from the Sync server first. And once you are done restart Firefox and then Connect back to the Sync server. One "issue" that I have with Sync is that when adding a new bookmark and when "moving" one or two bookmarks around, those changes are sent to the Sync server immediately; at the speed of light the new or "moved" bookmarks show up on another device or are moved on that other device faster than your eyes can focus on the browser window on the other device. But when you move more than two bookmarks quickly when rearranging them, Sync switches to what I call a "batch mode". Saving the changes to send as a "batch" later after Firefox "knows" that you are done rearranging your bookmarks. And I have gotten scrambled bookmarks far too often to be comfortable, since Sync never got the other device "caught up" on the other device even after waiting a few days to let them "equalize" on the 2nd device.