one of the many factors that stumbleupon uses to asses your ranking in their hierarchy of users is how many pages, photos, and videos you have stumbled. i recently discovered a stumbleupon-approved way of stumbling at light-speed.
by clicking tools > toolbar options and clicking through to shortcuts, you can set keyboard shortcuts for the various stumbleupon interaction options.
furthermore, you can go to the configuration panel from toolbar options and set your preferences so that based on whether you like or dislike a page (or both), the toolbar automatically sends you a new one without having to keep on clicking the stumble button.
once you’ve made these two changes, all you need to keep in mind are your ‘like’ and ‘dislike’ shortcuts and you can keep on stumbling without using your mouse.
note: it is also a good idea to ‘prefetch stumbles’ (from toolbar options > configuration panel) so that new pages don’t take extra time.