In playing around with Google Bookmarks, I've inadvertantly ended up with a slew of unnecessary entries. As someone has already mentioned to me, clicking on stars a bazillion times over can become quite a pain.
Here's a relatively painless means of clearing many bookmarks through Mozilla/Firefox, in case you ever want to start from scratch. You might like it, if you find my import/export tool unsatisfactory.
Remember, this is for Mozilla/Firefox based browsers.