It could only be Sony...
From the tech perspective I remember the Sony AIT product set, punted as the helical scan LTO killer. The roadmap was great in theory but the product was short lived because capacities grew and AIT couldn't keep up, albeit Super AIT which in itself was a linear technology and an expensive one at that too.
The Sony monitors, expensive and loved by those who has them on their desks, then like the flick of a light switch, Sony killed the product range overnight. The reasoning was the fact that competitors (LG & Samsung) were out pricing Sony, so they withdrew from the market hastily.
On the consumer side, Sony, as the Walkman / Discman pioneers had the portable / personal music market it their hands, but the Joker (Apple) marketed their MP3 player better and Sony again took a back seat in a market where they had every opportunity to continue their dominance.
The PlayStation was the cash cow for Sony, but competition from Microsoft (who's maiden Xbox sported a HDD) and Nintendo who wooed gamers with cheaper and (in the case of the Wii) simpler products that once again ate into Sony's once dominant market share
Sony's marriage to Ericcson gave them a great phone range, but niggling little issues like bespoke charger and interface cables ruined the product. I always like the Sony Ericcson phones for the sheer camera quality, but a smart phone needs more than just a kick ass camera.
Yes, Sony is a quality product, no denying that, but I believe they have also suffered collateral damage with the PSN hacking fiasco too. That in itself is enough to make a concerned (or paranoid) parent choose an XBox 360 over a PlayStation for their kids.
Perhaps Sony can pick itself up from this slump, the name reeks quality but the premium across the product range has consumers looking at alternatives.