I just posted an experience installing og on a multilingual site. The short version is that it ground to a halt because of the t() function. Maybe og is still a little early in it's 4.7 release, but I think it's an example of bad things happenning to good modules. Does anyone else have any experience, ideas about scaling t()? I can see there's some caching going on, and maybe I just need to adjust a cache size somewhere ...
[a while later]
aha, here it is: http://drupal.org/node/42463 - it's a problem with 'incomplete translations', and a proposed sql index fix didn't make it into 4.7 as per the discussion.
[another short while later]
yes, that made a huge difference:
alter table locales_source add key source (source(30))Conclusion: multi-lingual sites should add that index (and use a recent version of mysql) until it makes it into core.

Comments
Awesome
Thanks for following that all the way through, Allan.
locale enabled
multi lingual sites are all sites that use another locale than de default english...
other than that, I whish I had known this earlier :)
fixing the real problem?
in fact, adding that index improves performance, but there is still a coding problem that mysql is working hard to overcome here. Here's a forum article that talks about it and is currently working on a fix.