It is yet another of those things which, in the absence of reasons to believe otherwise, indicate that the environment is non-professional.  It is similar to cPanel and to consumer router/WAP/modem devices in this regard.

Regardless of what Oracle may say, it is totally unsuitable for infrastructure use.  It is (still) not stable, in addition to a litany of other indictments.

If someone is doing something with virtualbox like running production servers with it, they should probably be told to not do that, but the question doesn't need to be closed - just the answers they get won't help them abuse virtualbox for that.

If someone is asking about virtualbox because they are using it for labs or something the question should definitely be closed.  Similarly, if the problem is only a result of virtualbox being garbage, the question should probably be closed with a comment that virtualbox is garbage.

I don't see why we would want to fill the site with questions about how to do things that shouldn't be done, and answers telling people how to do things that will only cause pain later.

The only time we should be actually answering these questions with a solution about how to use virtualbox, I think, is if virtualbox is the user application being maintained.  It's a user application, not an infrastructure component, and questions about it being used as an infrastructure component should be treated the same way as questions about a linksys WRT54G being used as an infrastructure component.