Toyota is going through a rough time, currently, with all these break and accelerator issues. Self imposed, you may say, but maybe that's a bit too easy.
Why do such large scale problems happen? Here are four drivers/reasons I came up with:
1) What we see in car engineering is an ever increasing complexity and more and more interdependency between the different parts of a car thanks to the use of computers, bus systems and other electronics. This makes cars more vulnerable and maybe also a bit too clever at times.
2) People have increased their expectations for quality and reliability a lot over the last years. You wouldn't accept a car with major faults today anymore, while it was not uncommon that there were substantial flaws with cars in the past. When I had an Alfa-Romeo 164 in the early 90ies the accelerator also stuck and the car kept increasing speed. I had to break it down and kill the engine to fix the problem with the accelerator cable. But these things were not transparent. Many drivers in the 60ies and 70ies felt more like test drivers than customers.
3) Today we have an impressive ability to store large amounts of data, combine and compute large numbers of accident data and correlate/analyze this information. People share their opinions on the internet, report their problems in specific forums, blog about their experiences and find help in case of trouble. So, different to 10 or 20 years ago, major issues will not disappear, they almost certainly will pop up. And very quickly so!
4) Car manufacturers are forced to increase production efficiency and to globally source parts and pieces
to optimize logistics and cost. Well, this may not always lead to the best result. Which reminds me to a quote in the movie Armageddon: "You know we're sitting on ... 270,000 moving parts built by the lowest bidder. Makes you feel good, doesn't it? " (you can also listen to this here).
So, all these things together and a bit of a fading Japanese passion for quality and product perfection can bring you there where Toyota is today. And you can be sure that competitors will leverage the opportunity and make the best out of it.
Would I still buy a Toyota? I guess, yes, if they only made a really attractive car ....