i found this dnady of a quote with regards to digg and their front page. "It has been reported that the top 100 Digg users controlled 56% of Digg's frontpage content, and that a niche group of just twenty individuals had submitted 25% of the frontpage content." source here thanks digg. i guess its not really a place where the votes really count then is it?
My experience with getting top placement on sites like Digg and Reddit is that you get a huge amount of traffic and virtually zero leads, AdSense clicks or sales. It might help you if you're paid CPM for ads, but otherwise my experience says don't put a lot of effort into getting top spots...
Bum marketing is only a single piece of the puzzle. You have to understand that it is pointless to bring traffic to a site that can't convert that traffic into return visitors, customers, members, etc.
I'd rather get 100 ultra-targeted organic "ready to act" visitors a day than 10,000 bum rushing garbage hits. I'll make more money.
I wouldn't want digg for traffic, I like my articles at 40-100 diggs, so I get plenty of nice backlinks, without useless traffic. (Although getting the word out is nice).