Yishan Wong, an early Facebook employee, was the C.E.O. of Reddit from 2012 to 2014. He, too, had eye surgery for survival purposes, eliminating his dependence, as he put it, “on a nonsustainable external aid for perfect vision.” In an e-mail, Wong told me, “Most people just assume improbable events don’t happen, but technical people tend to view risk very mathematically.” He continued, “The tech preppers do not necessarily think a collapse is likely. They consider it a remote event, but one with a very severe downside, so, given how much money they have, spending a fraction of their net worth to hedge against this . . . is a logical thing to do.”
Ten months after the election, “Hillary For Prison” shirts have yet to go out of style, but what sells at any given show largely depends on what’s going on in the world that week. “I have noticed the radiation guys across from us this week,” says Mike Nocks, owner of Lebanon’s White Harvest Seed Company and one of the show’s guest speakers. “In years past, I haven’t seen much radiation stuff, but since the Korean guy has been doing more nuclear stuff, I’m seeing more interest in nuclear detectors.”
This group stresses being able to stay alive for indefinite periods in life-threatening wilderness scenarios, including plane crashes, shipwrecks, and being lost in the woods. Concerns are: thirst, hunger, climate, terrain, health, stress, and fear. The rule of 3 is often emphasized as common practice for wilderness survival. The rule states that a human can survive: 3 minutes without air, 3 hours without shelter, 3 days without water, 3 weeks without food. 
When bands of marauders start roaming the streets, how are you going to keep them out? Tear down a few walls, says Timothy Ferraro, a twenty-five-year construction veteran who's thought about this situation plenty while watching The Walking Dead. "Assuming the attackers don't have a battering ram, you should be able to keep them out using the lumber and drywall already in your home," he says.