IMO, one of Sony's biggest screwup was being very tolerant of poor quality...Looking back at the Playstation and then looking at the games other consoles were putting out at the time, it seems like Sony single-handedly invented shovelware, and left all future consoles to share the burden
Not so much a "screw-up" I suppose, but I've always hated the fact that when bringing games over to the US, they would always switch the functions between the B and the A buttons (or whatever they're called...star and trapezoid??). Through the SNES era, I was always used to A being the "okay" button, and B being "cancel", but for some reason, Sony of America didn't agree. I always thought it was just a changing of the times, but then I read on Wikipedia a while back that this is only a US thing, and the Japanese games are all fine. I'll never understand that one
Biggest biggest screwup though...Sony likes to use cheap malfunctioning components 
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I'll brave the storm to come, for it surely looks like rain...