No, what I was thinking, since they are using a database format anyway for Bookmarks, you should be able to search on the little descriptions or keywords in the bookmarks database(maybe not that great an idea since I don't have them all filled in, but if this worked then I probably would make a point of it when I saved the Bookmark.)
Say I had a bookmark to a site(fictional) named Histerocity but I can never remember what it's named because I only go there once a year. If the keywords or descriptions had the word collectables and I type in the keyword with some AddOn, it could pop up all the Bookmarks with that description/keyword. I have no clue how to do FF AddOn programming. I don't know how difficult it would be.
I have folders with most of my Bookmarks categorized but there's really more categories than room on the Personal Toolbar(and I've never seen a multiple row wrap hack that worked in FF like Opera has.) There tends to be some overlap. Like something could be Documentation but it's strictly Programming Documentation so it might be in either folder.
I guess the alternative would be to periodically export bookmarks as HTML and just load the page to search it. That might be easier.
edit: for now I exported the bookmarks.html and made a bookmark to the file on disk. I have to fill in more of the descriptions and keywords for it to be useful though.