Their robots.txt file clearly asks to not be crawled at all.
User-agent: *
Disallow:
http://digg.com/robots.txt User-agent: *
Disallow:
http://digg.com/robots.txt User-agent: *
Disallow: /
Allow indexing of everything with: User-agent: *
Disallow:
It seems they are at this very moment struggling to change things.