Yes, hair extensions, unless done by someone who REALLY knows the business, can be a disaster. So many of my friends have had horrible experiences with any type of fusion hair extensions, which is why they go with DIY clip-ins which they can control and monitor.
The worst experience I ever had was in 1988. I had been growing my hair for several years. Unfortunately I had also been using Clairol Nice n Easy color to keep my hair as blonde as possible. Unless you're careful with any box color, if you have any root overlap you start to have all kinds of issues.
My hair had grown to the middle of my back and then stopped growing. It wouldn't budge an inch.
I went to a guy who claimed to be a long hair expert. He promised to help me grow my hair to my waist.
The first thing he did? He cut my hair back to my chin. I HATED it and cried for days.
Eventually it did grow to my waist and to the top of my hips where it stopped again. Everyone has a pre-determined genetic maximum length. That is mine.
Was it worth getting all my hair chopped off? No. I don't care what that long haired stylist said. It was not worth it in the long run I believe there were other things we could have done instead of giving me the Big Chop.