I've never set one up on my iPhone 5 because I find it to be an annoyance when I want to check a text or a Facebook notification on the go. My boyfriend and I also are in the car a lot together and have each other respond to things when one of us is driving. It's just easier for us to not bother.
Quite honestly as a 20-something, my entire life is on the internet. I use different and complex passwords for banking, iTunes, Amazon, email, etc. But I try not to be paranoid about my phone getting stolen. What would a thief do? Send dick pics to my entire college campus?
If I lived somewhere where smartphone theft is higher, I might worry. But in a college town where smartphones are everywhere and I have Find My iPhone set up, it's not a huge worry. Seriously, my boyfriend lost his iPhone 5 in the KCI airport and got it back when he returned from his trip out of the country. It's not New York or San Francisco here.
As for my family members getting spammed, they use Yahoo email. They're already asking for spam without a thief finding it on my phone.