Every computer programmer, indeed anybody who uses computers extensively has been surprised by computers. Despite being deterministic, a personal computer taken as a whole (hardware, operating system, software running on top of the operating system, network protocols creating the internet, etc. etc.) is too large for a single mind to understand. We have partial theories of how computers work, but of course partial theories sometimes fail and this produces surprise.

This is not a new development. I have only a partial theory of how my car works, but in the old days people only had a partial theory of how a horse works. Even a technology as simple and old as a knife still follows non-trivial physics and so can surprise us (can you predict when a given knife will shatter?). Ultimately, most objects, man-made or not are 'black boxes.'