I am regularly asked what the average Internet user can do to ensure his security. My first answer is usually 'Nothing; you're screwed'.
It's frustrating; terrorism is rare and largely ineffectual, yet we regularly magnify the effects of both their successes and failures by terrorizing ourselves.
There's an entire flight simulator hidden in every copy of Microsoft Excel 97.
There are two types of encryption: one that will prevent your sister from reading your diary and one that will prevent your government.
When a big company lays you off, they often give you a year's salary to 'go pursue a dream.' If you're stupid, you panic and get another job. If you're smart, you take the money and use the time to figure out what you want to do next.
Air travel survived decades of terrorism, including attacks which resulted in the deaths of everyone on the plane. It survived 9/11. It'll survive the next successful attack. The only real worry is that we'll scare ourselves into making air travel so onerous that we won't fly anymore.
People don't understand computers. Computers are magical boxes that do things. People believe what computers tell them.
The user's going to pick dancing pigs over security every time.
You can't defend. You can't prevent. The only thing you can do is detect and respond.
It is poor civic hygiene to install technologies that could someday facilitate a police state.