I believe the whole operation of sending secret documents to wikileaks is done anonymously. Actually it is their job to make sure the source's identity is not revealed and their system is set up to insure it, otherwise who in his right mind would send them any documents of that nature?

But then their credibility is not that much, since you've documents that cannot be traced. For instance, some of what they've revealed form Iran sounds quite silly. Some we already knew. Some are just rumors that can't be either proved or debunked. In one report there's actually a number of votes for each candidate. In one it is claimed they didn't even count any, which sounds more accurate, but who can prove either of these without a source?