According to Tony Hung at Deep Jive Interests, top Diggers are routinely approached by PR types to help promote the companies they represent. As many of you will remember, Jason Calacanis first proposed paying the top users of social bookmarking sites when he started his notorious Netscape experiment. Digg founder Kevin Rose responded by saying that he would never pay top Diggers because it would contaminate the open and 'democratic' nature of the site.
From Deep Jive Interests:
... in talks with some Diggers, I have learned that some of themare routinely being... emailed with unsolicited requests from private companies to help them submit and promote their own stories., in exchange for money. The frequency is in around once a week or perhaps even more frequently...
Payment is either offered via a retainer or per submission, with bonuses given if the story makes Digg's front page. Mathew Ingram says that this is "more underhanded" than PayPerPost, which offers to pay bloggers to write reviews without requiring disclosure - and in theory I agree. The problem is that Digg is already a deeply troubled democracy, as all users are far from equal. It's a known secret that if a story is submitted by a top Digger it stands a far greater chance of making it to the front page, compared to a lower ranked user who submits the same story.
As Hung notes:
The irony, of course, is that there is already a fundamental sense of inequity between diggers, and this was shown by the simple ranking of Diggers - and the fact that top diggers’s submissions and votes are worth more than Diggers who just joined up. Changes in the algorithm has changed this somewhat, but the principle is still the same.