I found Metafilter through some random link in 2000. I lurked for a couple years and joined one day when I noticed that the sign-up window was open. I had just been reading a political thread where a rabid right-wing member denigrated another member for his/her "strange lefty double think." That, unfortunately, became my first username.
I quit a couple years ago after making a stupid stunt post that got deleted. (Sorry, no flameout.) I avoided the site for as many months (4 or 5) as possible and start lurking again. I could no longer remain silent and rejoined earlier this year.
If you love something, lurk for a while.
Metafilter really clicked for me after I quit the first time. I wanted to engage in a more thoughful way and felt I needed to step back for a bit. It was while I was lurking again that I realized how much the site made me happy, something that seems increasingly difficult for me to experience.
I was reading the End of Men thread (June 10, 2010) when rtha posted a comment about the top 20 careers for women in 2009. Soon after, furiousxgeorge asked if anyone had a similar list for men.
That was the cue to get my wheels spinning. I grabbed some paper and started writing what I thought would be the greatest favorite-getting comment of all time. I didn't keep the list but it went something like:
3. Race car driver
4. Nude model photographer
5. Lead guitarist
I also wrote a lead-in where I said that I was doing research on that subject, so that it sounded like I was serious at first. I got a great laugh out of creating my list but I didn't join and post. I was at work and by the time I finished the list in between other duties, the opportunity had passed. (fleacircus later posted the actual list for men.)
That moment made me realize the many joys Metafilter brings, especially while sitting in a gray cubicle in an bland office doing a job I don't enjoy. Metafilter keeps me sane.