Why did Digg die a slow and painful death? It depends on who you ask. In the wake of this news, nearly every major outlet credits Facebook and Twitter with delivering the killing blow. While both sites are large and have grown while Digg shrunk, to credit them with the destruction of the site is incorrect. Though both are technically “social media” sites, neither truly replicated the functionality of Digg as a vote-based news stream. Only one other site did: Reddit.
From what I see, Digg killed themselves while Reddit helped them.