Now this is something which I never know about digg. As per my knowledge a story on digg can be made popular (in other words getting to front page of digg) only with in 24 hours of its submission to digg. If a submitted story fails to reach front page with in 24 hrs of its submission, it dies its natural death.
But Tamar Weinberg of Techipedia reported that a story submitted by her 7 days ago is made popular today and is on front page digg with 942 votes (at the time of writing this post)
Here is that digg story.

Digg has got a legendary status among the sites of its type. A story gets several thousands hits in a day if made popular on digg. Because of this, digg has been a continuous target of webmasters. There have been several attempts to game digg like this one and this one.

Now as I can see, digg algorithm is getting more and more complex. I never expected that a dead story can reach to front page. The possible reason for this can be the multiple attempts to submit the same story by different users .
Seems like the number of attempts to submit the story by different readers is also taken into account by digg.
Anyways, digg algo is getting better, and we can expect great quality from digg.

Cheers.