Well, you can also encourage contributors to document their work. With Django, for example, our policy is that a submitted patch will not be committed unless it includes both unit tests and documentation in addition to the code.

This means it can take longer for a patch to be accepted, but it also means that the documentation stays up-to-date.

Absolutely. I think this is the real answer. Developers need to learn to document and improve their UI skills. To me those are core skills of a developer. We can't expect professionals in those areas to come in and rescue open source.