If you enjoy daydreaming about doomsday scenarios, consider this: nuclear power plants around the US and Canada (as well as the power grid itself) are vulnerable to serious attacks from hackers who could crash their servers, and screw with the regulatory systems that keep the reactors from malfunctioning and melting down.
Airport body scanners
Having to deal with the exceptionally unpleasant TSA every time you pass through airport security is bad enough, but guess what, it gets worse! Those body scanners that virtually strip you naked? Their imaging systems can be easily hacked, and your birthday suit could be distributed all across the Interwebs. Seriously, it happens.