commit: b67d552 - hire banner add for jobs on other sites (2014-04-23 08:56:43 -0400)
Doing the site:digg.com search myself, it looks like they did.
Matt Cutts just clarified via his Twitter that it was an "accident".
Whoops:) Maybe they forgot to uncheck the "de-index entire site" box.
it think it was all about the lolz, with Digg announcement it's releasing a Google Reader replacement. at least that's what i prefer to believe.