I thought this might interest some of you. I wrote to Hotbot saying that several dead URLs from my company's site are listed in their index and asked how to get rid of them, and this is what they wrote:
"First, regarding the dead URLs. The add URL feature is meant for new URLs that are not in the index, and resubmitting currently indexed URL can actually delay the update process. When the URL shows up on the queue, Hotbot will notice that it is already in the index and knock it off the queue. the best thing to do is wait for the spider to crawl your site and note that the specific pages are dead, and drop them."
So basically, if you're already in their index, resubmitting will not do any good.