2) As mentioned elsewhere in this thread, npm supports namespaced packages, but they are not mandatory. There are other major languages' registries in same situation.
3) Can you back up 'nobody'. I would suspect a lot of companies don't use a proxy. Some JS teams also use an internal proxy for npm, but it is obviously additional infrastructure to setup/maintain which has a cost.
4) Never heard anyone raise this as a problem before.
> Not directly related to the incident of the original post, but I was mindblown when I realized that you can unpublish npm packages
You can't, with the exception of a 72 hour window, to allow for accidental publishing [1].