Given this list, let me ask a trick question. What was the most damaging data breach in the last 12 months? The trick answer is: it's likely something we don't even know about.
When the Snowden revelations first came to light, it felt like we might be heading towards an Orwellian dystopia. Now we know that the situation is much worse.
Advertising-related surveillance has destroyed our privacy and made the web a much more dangerous place for everyone. The practice of serving unvetted third-party content chosen at the last minute, with no human oversight, creates ideal conditions for malware to spread. The need for robots that can emulate human web users drives a market for hacked home computers.