I discovered MetaFilter in 2002 at the same time I found Memepool, Waxy, and a few other sites. It was quickly my favorite, as the poo-flinging was kept to a minimum and intelligent discussion was encouraged over flame wars. The diverse userbase is what keeps things going.
You showed me that people care and saved my life.
I'd made many friends, both online and in real-life, after joining the site in '02. The most notable had to have been Franny (Pomegranate), who Mefi-Mailed me one day and said "Hey! You don't know me, but we're neighbors!" - she lived 3 blocks away! My wife and I met Franny and her family and they became good friends.
However, the moment that MeFi "clicked" had to be when my wife passed away suddenly and unexpectedly in June of '09. A few days later, I posted to AskMe about my general feeling of "What now?" and how to deal with things.
People started COMING OUT OF THE WOODWORK. Tons of MeMails, normal emails, postal mail, virtual hugs - you name it. I was surprised at the support I received from my fellow MeFites, even if they'd never met me in person and only interacted with me online. I started getting things in the mail - books, Kinder eggs, cards, messages of condolences, and even a postcard from Jessamyn.
I talked to other widows and widowers, got in touch with online support groups, and was reassured that the strange feelings and emotions and sense of absolute loss I had were *normal*, that I wasn't broken, and was warned about stages of grieving and what to expect. I made many, MANY new friends. I got weekly bagel deliveries and hugs, from Pomegranate who was just checking up on me.
A month and a half later, I posted an update on the situation and how I was doing. In the discussion it came out that I still owed money for Amy's ER and ambulance bills. Matt asked how much I owed, and shortly thereafter, an adequate amount of money to cover those expenses showed up in Paypal. This enabled me to pay those bills and get one more monkey off my back.
Even today, two years later, I get occasional MeMails, IMs, and so forth from someone I met on or through MeFi. "Hey, how you doing? Thinking of you. We care."
I can say in complete honesty that the support, friendship, companionship, and caring I received from members of MetaFilter saved my life and kept me from ending my life due to depression after the loss of my partner of eleven years.