After quitting (or, depending on whose account you're reading, being forced to leave) from Wikileaks, Domscheit-Berg created a project called OpenLeaks and wrote a tell-all book: "Inside WikiLeaks: My Time with Julian Assange at the World's Most Dangerous Website."
An extensive statement on the matter from Julian Assange is here. From a quick read, he appears to believe the CIA is behind this, or that Domscheit-Berg is connected to the CIA in some manner.
Update: The Spiegel article is online. Wikileaks' Twitter account (presumably Assange) tweets that the purportedly deleted data included a complete copy of the US no-fly list, 5GB of Bank of America documents, leaked data from neo-Nazi organizations, and intercept data for US internet companies, then solicits financial donations.
Former Wikileaks spokesman Daniel Domscheit-Berg claims to have destroyed more than 3,500 unpublished files that had been sent from unknown informants and are now apparently lost irrevocably. These are documents which were stored until the late summer of 2010 on the Wikileaks server and has taken a group to Domscheit-Berg in their leaving the organization.
He had the files "in the last days shredded to ensure that the sources are not compromised," said Domscheit Mountain. Reason: WikiLeaks founder Julian Assange could not guarantee a safe handling of the material.
In the data base was located on SPIEGEL information including the so-called "no-fly list" of the U.S. government, on which the names of suspects were listed, which is prohibited from entering an aircraft. Assange said of the material would also have insider information from 20 right-wing organizations is one. Domscheit-Berg would not confirm that. Assange calls since the beginning of the publication of the data
Boing Boing editor/partner and tech culture journalist Xeni Jardin hosts and produces Boing Boing's in-flight TV channel on Virgin America airlines (#10 on the dial), and writes about living with breast cancer. Diagnosed in 2011. @xeni on Twitter. email: email@example.com.