Re: Can you multi-site BuddyPress?
BP_ENABLE_MULTIBLOG basically allows BuddyPress to not look for the root domain, but instead just work on which-ever domain or blog that you’re on at the time. It isn’t really the answer to this question/issue, but rather a way to side-step the issue.
At the moment, there is no kind of “BuddyPressMU” type setup, allowing multiple BP communities on one installation. But, this isn’t an impossible task to pull off, with some effort. 
The underlying problem is that BP uses 1 set of site-wide tables for all MU blogs regardless of site or association. It is coded to think that it has control over the entire MU setup. What would need to happen is for BP to look for which site it is occupying and enumerate its DB tables according to the site_id…
However… If we’re using one MU installation, we’re still talking about sharing a userbase regardless, so even the above scenario might not be optimal. Ultimately the problem comes from the shared userbase, which means even a new “site” has no real way to say these 10 users only belong to this site, and these 12 users to this one, and these 20 users to this one…
Something like this, in my opinion, is something that the core should be aware of, but not manage; similar to sunrise support in MU. As setups like this become more popular and the community need for it arises, I’m sure there will be a great solution to this.
