I was sitting in a bar in the airport on my way to Ireland and met another traveler heading the same way. We thought it was a funny coincidence until my friend pointed out that it was the only bar in the airport that was open, our flight was the only one using a gate near the bar, and it's not terribly unlikely that people taking a short vacation in Ireland would find comfort in an airport bar. Then today I was wishing I had the bands I use to keep my pant cuff out of my bike chain since it's getting too cold to roll my pant leg up. Then I fished in my jacket pocket on the way out of work and found the band. I thought it was quite a coincidence until considering that I hadn't worn the jacket since it was cold enough to need it on a bike ride. I'm sure that the vast majority of coincidences share similar cause/effect relationships, but most of them are just slightly beyond the veil of basic logic. Next time I randomly run into someone I know I'm going to badger them with questions until we figure it out.