This happened to us with a couple who were very close friends for a number of years.
DH was originally friends with the DH at school, DH was best man at their wedding, I'm their daughter's godmother. We went on holidays together, spent loads of time with each other, we looked after each other's children, our children were great friends.
Then we moved away - DH was offered a brilliant job opportunity, but it was the other side of the country. Regular hours, more money and the move gives us a brilliant lifestyle - we live right by the sea, the kids love water sports, etc.
When DH first got the offer, they tried to talk us out of it. Told us we were stupid, we'd regret it and be back in 6 months.
That was getting on for 10 years ago now and we haven't heard from them since.
The first year we moved we went back for Christmas and tried to get in touch as we had some presents for their children and our kids were desperate to meet up with their friends. No response at all.
We tried to get in touch several times the first few years but they never replied to messages or returned phone calls so we've given up.
A few years ago we were back visiting my parents and we bumped into them in town and they completely blanked us. We said hi, and they both walked right past us, they had definitely seen us as their daughter pointed my eldest DD out.
We spoke to some mutual friends about it once and apparently these friends didn't approve of our move and felt we'd ignored their advice so we had made our bed and now had to lie in it.