He's right, it varies on several factors. For example, I have one story with 62 diggs, and still in upcoming.
Digg uses an algorithm which determines if a story is popular (to get in front page) based on the number of Diggs in a period of time for a particular category. a story could be in front page even with 30 diggs(as Eli B said), it's vary and depends on the category and period of time. - DarkX
Incorrect. They just have an algorithm, or whatever. If an older, more trusted user diggs a story, it's worth more than a new users digg. For example, if Kevin Rose submits a story, or even diggs a story, it will definitely make it to the front page Now that's not very good (so I've heard, anyway)
"based on the number of Diggs in a period of time" I thought this was quite self-explanatory. If you can get 30 diggs in 15 minutes you stand a much better chance of being shown on the front page.
I swear that once I saw an article hit the front page with 9 diggs. It all has to do with whoever diggs the articles and how quickly. If senior members there digg your article under 3 minutes, then you could hit the front page really quickly.