Web browsers have had bookmark bars for years, but I never used them until I switched to Google Chrome. I’ve always felt that the amount of screen real estate they consume is too great compared to the number of bookmarks that will fit (and I dislike having all my bookmarks in folders).
What made me change my mind was icon-only bookmarks. When adding a new bookmark in Chrome, delete the Name field – leaving it empty. Chrome will insert the bookmark using the favicon provided by the website. As long as these icons are distinct, you end up with a compact bookmark bar.