All I can say is THANK GOD that I did, because it turned into over a week long effort to get them out. Two decided to walk out and were able to text me a nav point that I was able to meet them at (took all day to get there because of the snow and mud, but I made it and was able to pick them up). The other two stayed up there, and we sent probably 100 texts back and forth coordinating what turned into like 3 solid days of fighting to get up there with snowcats and get them back down. Multiple situational changes that we would have been hosed without.
In the end, I spent like $80 on texts, but it was money well spent. I think it's great for people to have SOS built into their iPhone, but there needs to be a "use it now, pay later" or no one is going to activate it and actually have it available when they need it. The other half of the equation is that you really need to be able to send texts. The SOS button is very expensive. Extremely expensive. That will keep a lot of people from using it. (Yes insurance exists, but hardly anyone has it). Being able to text your friends for help is substantially more useful. Being stuck on a backroad with no service, 5, 10, 20 miles from where anyone can be expected to drive by is a far more common scenario than breaking your leg at the top of a mountain and needing to be evacuated.