XKCD will hit the front page of Digg. Every time. No exceptions.
The often brilliant webcomic XKCD is published on particular days and at particular times during the week. The clockwork nature of the posts is followed by several Digg users because every post will hit the front page. The chances of a Kevin Rose submission missing the front page is higher than the chances of XKCD missing.
As a result, every post is submitted multiple times within seconds after it goes live. Because Digg does not “lock out” submissions once they are started, everyone who starts submitting before the first one is completed will be able to continue their submission.