Superphish showed us that Dell is clearly willing to do something of that nature, but the data the hackers are alleged to possess (shared secrets, support histo

Superphish showed us that Dell is clearly willing to do something of that nature, but the data the hackers are alleged to possess (shared secrets, support histories, ...) isn't the kind of thing you'd sell. There is no proof, but there the author certainly presents plenty of evidence. Unless you have access to information outside this article, the most likely hypothesis is that their database was compromised.