Stasiland http://en.wikipedia.org/wiki/Stasiland is a fascinating read. And of course "The Lives of Others" is a must watch. If for no other reason than to experience an eloquent demonstration of powerful yet understated acting.
http://en.wikipedia.org/wiki/Secret_files_scandal
The Stasi is a fascinating example because the fall of the GDR was quick enough that they couldn't destroy most of the existing files and evidence and we have a relatively clear picture of what happened there. For the Swiss files from the 80s, an official archive exists but access to actual data is relatively difficult. If other democratically elected governments practice Stasi-style surveillance, it would be extremely hard to find out (and would, arguably be the bottom of an iceberg ranging from regular law enforcement to espionage and counter-espionage, to proactive intelligence gathering to find likely terrorists, to proactive intelligence gathering on random citizens who are not terrorists but may have rented a car from a suspected terrorist's relative).
Note that Lawful Interception (i.e. interfaces for government agencies to siphon off data from internet providers), as it was established by US and Europe, was never a focused effort to provide data for criminal investigations but started out with different groups of users in mind (i.e., espionnage and possibly other uses that the average citizen would find spooky).
And, as the article explains, the same technology that is used to guarantee Lawful Interception in Germany/US/other countries is used for political suppression in countries that would perhaps lack the technical sophistication but have a budget and corresponding sources for these. (Although I'm reasonably certain that companies in China and Russia will be happy to provide similar technology to potential buyers).