Don't get me wrong, there are failures, Ping, or MobileMe being some examples, but I think that is the result of not trying (and learning) enough.
For example, it is said when designing the iPhone they tested (tried) two different operating systems, one based on OS X and the other one based on Linux. Even the hardware itself was first started as an iPad like device and was later decided to shelve the original project and do the iPhone instead. When you try an idea you learn, and you might even learn that it is a bad idea. I don't think of that as failure, the only failure is to not use what you learned. I'd be worried if they, despite the knowledge gained and to not be thought of as a failure by pundits, decided to be courageous and go to market anyway.
The article refers to the secret car project that was never launched. It is fairly likely that in Jobs' time there were a fair amount of cancelled or downscaled projects as well but we just haven't heard of them. For example, the TV comes to mind - there were a lot of rumors about it at the time, and it was mentioned in his biography - and nothing came of it.
But maybe that is why I'm no analyst.