Sgt_Kickaxe - 8:51 pm on Jan 9, 2013 (gmt 0)
In WMT Google told me that there was a software update for vBulletin recently (when I've never seen before), so they definitely know it's a forum.
Google doesn't need any rich snippets or meta data to spot a forum or CMS and they did warn everyone some time ago that they may not trust your site as much if they detect that you aren't keeping the code up to date.
I've caught Google attempting to load backend pages that are never linked from anywhere (I am the only one to see them and I don't use Chrome or have a google toolbar etc). For wordpress they seem to check the remote posting page a lot(xmlrpc.php), perhaps to see if I have it disabled since it provides a different error message when disabled and poses a small security risk when enabled.
I've caught Google requesting that page on a static site as well that doesn't even have a CMS system. I believe Google is equally interested in knowing if your site allows anonymous user content to be generated which might also be why they keep checking that file.