Andrew talks about lots of software engineering-related stuff but his comments on code reuse got my attention.

What we really need as software engineers is a way to say succinctly what a function does - what goes in and comes out. Then you need the tests to back up that this function actually does this and other software engineers can then independently verify it.

If we have a system people can depend on we'll probably find that there will be more code reuse. As it is now no one can trust anything anyone else does.

As for code ownership -- you need some variant of it. One person has to be able to control what goes in and out of any given part of the code or there will be anarchy. I'm personality an advocate of code supervision ... people can change everyone's code, but they better not piss any of the supervisors off along the way. Accountability is an important aspect of group work -- it keeps people in check -- and it also works very well for open source projects.