Just an observation (and I wasn't even sure where to put this topic, but figured 'relationships' was close enough).
Over the years, I've been defriended on the rare occasion for unknown reasons. Some really leave me scratching my head and wondering what I did wrong!
Number one - a girl who I was pretty good friends with at one point. We met at work and hung out occasionally in our spare time. Got drunk together, I stayed at her place, she stayed at mine. We are similar personalities, introverted but with a keen sense of humour. Lost touch but then reconnected via Facebook. She was working at the same place we first met, but had gone to India for work (training people up over there). I left a few comments on her pics of India, all seemed well. Then she came home, left her job and updated about that on FB. I left a (what I thought was innocuous) comment on that post, saying something like, "Welcome home, glad you enjoyed India, what plans have you got now?" Then a few days later I noticed it said "Add friend" on her page!! I don't have a clue what I did wrong but we haven't spoken since. Maybe I was too nosy?!
Person B - a guy I met on a tour I went on in Africa. When I met him he was on his honeymoon, and as there were only 4 of us who were under the age of 50 on this tour, we all kind of hung out together in the evenings. Nothing wild, just chatting about our lives over a glass of wine. The other single lady there (my Scandinavian roommate) told me that the guy's wife had made a funny comment one night, insinuating her new husband would try to cheat with her. Bizarre. Anyway, we all came home and added each other on FB. A few months down the line and the wife had defriended me. No idea why but there you go. She also broke up with her husband very quickly and found a new man. I would occasionally comment on the (now ex) husband's FB page and he on mine, as you do. Was still friends with the Scandi roommate. Then one day the guy left a photo of his new kitten on his page and I left a comment saying how cute it was. Next day I noticed he'd defriended me! Just seems quite random to me.
No 3 - another guy, this time someone I have never met. I met his sister while travelling in their country years ago and houseshared with her for a few months. Came home, added her on FB. Several years later while I was bemoaning the lack of nice, available men in this country she joked that I should date her brother, because he's single, and nice. Of course being so far away that was next to impossible (although my now fiance lives in the same country, ha) but we added each other on FB anyway, because she said we should. I didn't actually chat to him much, just left the occasional comment about his dogs etc. Just the odd, chatty comment. Sometime later he started dating someone, good for him I thought. A little later I realised he'd not posted or commented for a while, so thought he must have deleted his profile, fair enough. I even wondered if he'd fallen out with his sister, as she once spoke about how her family had abandoned her. I never said anything to his sister about it, it just made me think 'hmmm'.
But here's the weird thing. The sister posted on FB tonight and tagged her brother in the post. Except there was no hyperlink. Someone else commented and mentioned her brother's name and someone liked the post. But, I can't see who liked the post. So it seems like he's blocked me! Either that or I thought he was somehow able to have a hidden profile. But when I log out I can actually see his profile so it seems like I was blocked!! lol No idea why because I barely spoke to the guy! 
I could see defriending for whatever reason I guess but blocking me seems a bit extreme. The only person I've come close to blocking was an alcoholic former colleague who would get drunk and leave suggestive comments on my page. I was embarrassed at what people would think but in the end I just defriended him, and told him I wished him well but couldn't watch him destroy his life anymore, also the comments were inappropriate. He said he understood. So I've no idea why that other guy has blocked me! Maybe his girlfriend made him do it (although I have no idea if they're even still together).
Maybe some people are just weird. It makes me a little paranoid though, because I'm nice! Maybe I'm too sensitive, I want people to like me. I'm not hugely upset about this I'm just a little surprised and wondering what the reason was. I don't think I put anything offensive on FB, holiday photos, the odd jokey post etc.
Anyone else have this happen to them?