Lets say a user post in english on a danish forum.
Then we have a danish link .../da/showthread.php?t=xyz... that contains English text translated to danish (you can show the english text using the "drop down arrow").
Then if you search for an english string from the translation the danish link shows up, because Google indexes the english text that apperes in the source of .../da/showthread.php?t=xyz...
So what we need is a tag that tells google not to index source content. Otherwise you can run into problems with duplicate content because the same source content will be indexed in 52 different links.
Example: I have a buyer who consistently buys only R from me and he site:www.thegame-online.dk - Google-søgning
PS Seems external direct is not working properly on this forum, at least not in explorer ...