We do encourage this in our employee-only community for the reasons you state above. Also, Google Translate has plug-ins for all three main browsers, so that is an option to suggest to employees who might want to collaborate in these areas but can't natively read. It obviously isn't perfect, but you can get a general gist. We're also hoping that someone will create a widget for the Jive Apps studio that will do translation.
Hope this helps!
I think it's a good thing as well. Any collaboration is better than no collaboration. the people that need to collaborate on subjects that are international will naturally do it in english. What would be useful is to encourage local people to translate and link content that they think would have a broader scope. It will also be helpful if the Japanese and others at least try to tag their content using english tags. than at least it will show up in searches.
Agree with Bart and Tracy. The only thing we do is try to watch the creation of those groups and discourage groups on the same topics from showing up in multiple languages. Not doing so creates more silos that slow down the diffusion of knowledge across the company. For example, if we have a product or service that is sold and used the same way around the world, we try to ensure there is only one group that all employees can join to stay informed and collaborate.