i just want to know because i am trying to set a goal for mysel for the new year. and i have to know how hard i have to work.
Digg doesn't run adsense. They are so big now they directly negotiate with companies like google etc. The last I heard they had hit an advertising deal with microsoft.
Digg is not only using adsense. They will have some contract with comeany like MS or google. They fight to get chance for using the ad network in Digg because of the huge traffic.
Once you're big enough you don't use the 'standard' means for advertising. Every big website on the Internet has a contract with one or more companies to directly advertise their products/services.
...Anyone wanting to match their goals with Digg's is pretty ballzy, IMO. As wmtips mentioned the costs are pretty large as well. They make a ton from ads, but it's only relavent to their budget. If you can manage it properly with adsense at first, then move into Private ads, you got a shot. My hat's off to you! Good luck