I'm not sure it will work at all. Bots don't trigger the submit event by clicking a button. They do so by scripted form submission, so if the slider is tied to a simple submit event, it's pointless.
I haven't tried circumventing their form, and maybe they didn't do this, but the basic idea is to store the submission URL in javascript, and assign it to the form only on the slider event.
hell, a regular firefox browser with images disabled (for speed) and the selenium plugin installed could probably accomplish a high rate of automated spamming.