Digg caught gaming its own system, claims it was just a test
The 159 dummy accounts all have obviously-fake names (such as the "dd1" pictured), and they curiously seem to have only contributed to submissions from Digg's publishing partners. The suspicious activity began after an algorithm revision that took place on October 15.
The submissions that the dummy accounts helped get to the front page do not represent a major percentage of the stories that made it to the front page, but the fact that they were all links to Digg's commercial partners makes this all the more suspicious. If Digg isn't behind these accounts, then it surely chose to ignore them, since it's unlikely that their activity would go unnoticed.
The methods used to collect this data and the data itself is available from Digg user LtGenPanda on his blog.
Digg has issued a response to these allegations, stating that Digg employees were indeed behind the dummy accounts. Digg claims that these accounts weren't built to game the system, but to test for vulnerabilities that may lead to influencing how stories appear on the front page. Apparently, these accounts created a big learning opportunity for Digg staff, and they've prompted some changes to the code over the past few weeks, with more tweaks to follow. Digg founder Kevin Rose himself took the time to stress that Digg has been doing such tests "since day one" and that Digg never received any money from any publishing partner for anything other than standard ad units.