Tonearm - 6:56 pm on Feb 20, 2009 (gmt 0)

The only way to truly "fix canonical issues" for real (as you like) is to check all incoming query string parameters, and if any invalid ones are found, issue a 404, or a 3xx and redirect to the correct page. However, that would make most of my search marketing and SEO customers cringe as it kills most of how they track things, including inbound referrers (depending on the 3xx code.)

Just check the user agent. I don't think that would be considered cloaking would it?