So, I have been using the Xmark extension to store my Google bookmarks in the cloud for awhile and love the extension. I have been sharing the bookmarks across several computers, so I love the convenience. I had noticed in the past few weeks that my bookmarks kept getting duplicated; duplicated duplicates of duplicated bookmarks, lol! And of course, deleting them one by one would take me a million years to do, so after some research, I discovered a fix! I hope this thread will be useful to Google Chrome users as a reference if you happen to have the same issues with your bookmarks as I did mine.
Step one: I went into my Google settings, clicked on "advanced sync settings" and changed the option from "sync everything" to "choose what to sync". From there, I unchecked bookmarks. This disables Google sync.
Step Two: Since I wanted to get rid of all the duplicates, I had to basically delete all of my bookmarks and start over, so I found where Google Chrome keeps its bookmark file. Under Windows 7, go to Computer - Local Disc - users - [username] - AppData - Local - Google - Chrome - User Data - Default. In the default folder, you'll see a file called "bookmarks". Delete that file and it will erase all of your bookmarks. In Windows XP, goto My Computer - Local Disc - Documents and Settings - Username - local settings - Application Data - Google - Chrome -User Data - Default. Again, search for the file called bookmarks and delete it.
Step Three: Click on your Xmarks extension, log in if need be, and re-sync your Xmarks bookmarks. You should have your bookmarks back that was saved in the Xmark cloud. By the way, even before doing any of this, you might have to first log into the Xmark cloud and get rid of the duplicate bookmarks if they happened to get duplicated in Xmarks as well. This was actually the "pre-step" I did before doing the rest. Once I did that, the rest worked pretty well.
So now, I don't use Google's built-in sync system to sync my bookmarks, I just use Xmark's extension. You may ask why I even have Xmark if Google syncs everything on its own, and my answer is that I have had the extension for awhile now, and I'm not sure if Google Chrome had a built in feature to sync bookmarks across other computers before, so that's why I have Xmark. It's possible that you could just use Google's sync feature, but if the bookmarks are already duplicated, and you delete your bookmarks, I'm not sure if you can get them back any other way, so I feel safer just using Xmark.
Anyways, I hope this might help someone out there in cyberspace.