I write programs that are used in operating industrial facilities, and I used to think that iterative development was ill-advised under those conditions because it would be too easy for things to go wrong.

Over my career, I have shifted towards iterative development. I think the change in the way I develop applications has come about because I have a much better feel for where things can go wrong, and I have learned that you can never fully anticipate where problems will arise.

I still have some reservations about freshly minted developers working iteratively, mostly because I fear that there are some things they will end up learning the hard way that more seasoned developers wouldn't make. I think that risk can be successfully mitigated by having junior developers work with mentors.