I lived in Walnut Creek, CA, from 1957 to 1964, then my family moved to Richmond, VA. In 1971, I enrolled in college in Boston and was randomly assigned a roommate. When I met him, he mentioned that he was from Concord, CA. I told him that I used to live in Walnut Creek and we started to wonder if we knew any people in common. The very first person I mentioned was Janet S. (a sort of unusual last name, but not very), a girl I had a crush on in the fifth grade. He responded, “From Walnut Creek? She was my date for the Senior Prom this Spring!”
I recently found out that a friend I’ve known for 10+ years and a new-ish senior manager at my company used to work together, and were both in the Pentagon on 9/11. I made the connection after hearing the manager’s 9/11 story, and realizing that it sounded very similar to my friend’s story.
I have a Dope-related tale:
About a decade ago, I’d been interacting a little with Gadarene – I think there was even a DopeFest in DC that he organized but didn’t attend – and connected with him on LiveJournal. One day I started looking at some of his friend’s journals, and wound up connecting with a guy named John. Several months later, I was reading a post from John where he mentioned being at a Nationals game and yelling certain chants with his brother and barely missing an unusual fly ball that went just over his head…and I realized that his seats were just one section over from where my ex and I had season tickets, and that I’d been at the same game! We met IRL at the next game we both attended, and after my ex and I broke up I started occasionally using one of John’s extra partial-season tickets. John and I are still friends (though these days the online connection is via Facebook), and we went to a Nationals game together as recently as this postseason. I’ve still never met Gadarene, though. 
In 2010, I started work at a mail order Pharmacy. I befriended a co-worker and we shared rides to work together. 5 months later, I met a woman on a Dating site as, she was deleting her profile ‘tired of crappy guys available online’. She and I got married in September 2011 and, I invited my work friend to attend the wedding. My Brother was supposed to be my ‘Best Man’ but, he was unable to attend because he was sent to England. My wife’s brother from Pennsylvania stepped up to be my Best Man. The day of the wedding my co-worker and my best man met in the lobby of the Church and, they knew each other from Elementary school. They attended the same Church in Pa. and, my wife being 8 years younger did not recognize the last name. Talk about coincidences all the way around.