Art by the same submitter submitted in rapid succession gets pushed back 24 hours temporarily. Spammers submit like that to saturate the front page with ads. This gives me a chance to remove it without it getting picked up by seo indexing crawlers. 

In the case of non spammers, it gives everyone else a chance on the front page instead of being immediately pushed off by one submitter. If you're submitting a lot of similar stuff that works well together, it is better to submit them as a set or album on one submission instead of, for example, 6 different submissions containing one sprite/texture/song each.