After the wall came down, the stasi shredded a lot of their files. But they were reassembled a few years ago and they revealed that some of the dissidents at the time were snitching on their fellows in return for less harsh treatment.[1]
I don't think Schneier is similarly compromised - to give out misleading interpretations of the NSA leaks - but we can't know that with 100% certainty as long as the documents he's commenting on are not public.
It's a little offtopic, but those shredded files were put together with software (they scanned all the scraps and put them back together with algorithms).
Here is a link to the research article (couldn't find a free source, sorry): http://link.springer.com/article/10.1007/s00287-004-0395-8
You don't even need computers to piece together shredded work. Iran pieced together the shredded US Embassy documents by hand, and China pieced together shredded Soviet atomic bomb documents. You just need time and lots of people. Shredded material is often not well-mixed, so there is a great deal of spatial locality.
The thing that distinguishes the Stasi case is that they produced a lot more records, and German workers cost more than Iranian or Chinese workers. That's where the computers came in.
These days, with cross-cut and confetti shredders, the computers would become even more important.
Maxwell brothers spring to mind. Panicking and using a single cut type shredder to shred documents after Captain Bob's demise. I gather assembled piece by piece over months by UK forensic science employees.
I don't think Schneier is similarly compromised - to give out misleading interpretations of the NSA leaks - but we can't know that with 100% certainty as long as the documents he's commenting on are not public.
[1] http://articles.latimes.com/2009/nov/01/world/fg-germany-sta...