What killed Digg though, wasn't any change in look at feel, as much as a fundamental change in content policy. It went from 'users submit stuff and upvote it' to 'content publishers can automate a firehose of their stories into the system for a price' people didn't like that.
I'm seeing a similar parallel to Reddit's new profiles though. Not exactly the same but it's a move to appease the content publishers that has been angering their core userbase.
The way I remember it, Reddit had pretty much already beat Digg by the time they attempted the redesign and pivot (which largely went hand-in-hand). Those changes were just the final nail in the coffin. But as far as Digg was competing with Reddit, Digg hat already lost.
For me Digg's real problem was that a small cadre of politically active users figured out how to hijack the site and steer it the way they wanted. That's why I left. Reddit did a way better job of sandboxing those people.
