I found MMM around the start of this year, shortly before I turned 23, but the foundations were laid long ago.
I'm one of four children, and my parents always emphasized budgeting and talked openly about the balancing act between things like sending us all to Catholic school (their priority, not mine) and their occasional unemployment or falling back on freelance work. We dealt with money being tight sometimes but we always enjoyed a solidly middle-class lifestyle, including our share of car-clowning. It still got me wondering when they'll be able to retire, and I spent most of high school and college watching the recession and the long slow recovery.
Other positive influences: A friend in high school who introduced me to the bus system, a group of friends who focused on just hanging out rather than going out and spending money, and my longstanding attraction to thrift stores -- albeit to collect lots of music and electronics I've spent the past year downsizing!