I frequent Digg.com - it's nice.
One thing though, I wish Diggers would be moderated in the same manner as the articles. Thumbs up - or thumbs down.
That way, when I see that someone has befriended me, I won't have to spend much time wondering if it's a robot or someone that has the slightest interest in what I'm Digging (robot: someone that just adds as many people as he possibly can)
The simplest way to implement this would be thumbs on the person's profile - another nice-to-have would be the popularity tally of the digger's comments (although robots usually don't comment)
This would be similar to /.'s karma (uh-oh I said it) but more in the spirit of Digg - seriously, there are some Diggers that desperately need to be Dugg down. Imagine if you could simply automatically block the comments from users with a negative 3000 Diggs.