It's not just phones. I've had their TVs (old CRT and flat panels) fail within a year of purchase. A camera with a zoom lens that didn't work out of the box. A microwave which only displayed 99:99 on the display and wouldn't turn on. A washing machine where the hoses to the outflow pump came loose and flooded our kitchen. Luckily I didn't have to deal with Samsung directly and sent all that stuff back to the retailer to sort out, but I did learn a lesson.
As for their phones, they just seem to be a little bit more delicate than other brands. Things like the glass seemingly being easier to break, charging ports getting loose and not allowing for a good connection and physical buttons that just fail.
I know other peoples experiences will be different, but for me I have decided to never again buy Samsung.