It isn’t like you don’t end up with some degree of centralized organization, or at least with a central core of contributors. That in itself isn’t a nice I obstacle, but if that core group ends up being core because they’re willing, rather than capable and good at the job, that becomes a giant problem.

Oh, for sure. It isn't perfect, but it begs the question of what the end-goal is that one desires. A similar argument could be made for open source software. One could argue that it is less efficient, and you potentially get people that don't know what they are doing contributing. But, to me, the end goal is about ensuring openness rather than perfection. The openness, itself, is the end to the means.

At least the OED can be said to be handled by people that know language, and English in specific.

To be fair, though, nothing is stopping such types of people from also contributing to something like Wikitionary.

Besides, as soon as any dictionary becomes used by enough people, it becomes an authority. That’s unavoidable. Open sourcing doesn’t prevent that, and then you’ll still have people treating it like the dictionary is the authority rather than being a repository of language as it exists and changes.

That's a fair point, but I would ask if one would prefer an oligarchy, or a democracy.

Every major document dictionary, including the ones mentioned here, follow the changes, they don’t force them. The reason they’re authorities is the long time they’ve followed language successfully and in timely fashion.

That's a fair point.

The real importance of a dictionary isn’t private vs open, it’s the skill involved in writing the definitions. That takes a good bit of work to develop.

Technologically, it is also worth mentioning that, often, open services come with the added benefit of an open API. This allows people to make their own dictionary apps and services rather than having to pay for private API access to some proprietary dictionary service.