I have several tens of thousands of bookmarks in Firefox. Whenever I accidentaly hover over the "Bookmarks" entry of Firefox menu in global menu, my whole desktop freezes for half a minute.
Now, I know the obvious solution is "less bookmarks". But that is a workaround. I actually consider this a bug, because when an app cannot handle X amount of Things, it should disallow a user to have more then X things :).
But for now, is there a quickfix?