Pan,
There seems to be something wrong with either the configuration of your server or, if you're using a 3rd party SEF extension, the configuration of that. Basically, Facebook will add on the extra query string parameters automatically. There's no way to remove them. They are used for your site to be able to track certain types of visits (Is this user coming from a Like?) and do other things like that with the information about the referral of the user from Facebook.
On your site, however, URLs with a period in them seems to throw a 404 error. If you take the URL you gave me and simply change the "og.likes" text to "og-likes", the URL works as expected.
I'm not sure what would be causing periods to go crazy. It could be something with your .htaccess file, your overall Apache configuration, or (like I mentioned) an SEF extension (not core-Joomla) that doesn't like periods. We've seen the SEF-extension problem on Joomla 1.5 sites, but they're not as commonly used on 2.5, so haven't heard of that issue as much there.
Hope that helps you start investigating. Unfortunately, there's no way to instruct Facebook to not insert those query string variables, so you'll need to find the cause on your end.
Good luck,
Alex
Joomla 2.5 link redirect problem
