Some references below:

Mailing list archives
A workaround would be to build both the canonical and non- canonical URLs and compare them with the requested URL. What do you think? ...
mail-archives.apache.org/mod_mbox/lenya-dev/200309.mbox/%3Cbk7j9g$f9i$[email protected]%3E - 5k - Cached - Similar pages
greimblog
</p> <p> Another problem with non-canonical URLs is in web analytics. Two versions of a URL might really be the same page, but a web analytics package ...
blogs.sun.com/greimer/feed/entries/rss?cat=%2FWeb+Design - 20k - Cached - Similar pages
Gregory Reimer's Weblog
In fact, any caching system is impacted by non-canonical URLs. Another problem with non-canonical URLs is in web analytics. Two versions of a URL might ...
blogs.sun.com/greimer/?page=2 - 35k - Cached - Similar pages

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Note added at 1 hora (2007-01-23 01:42:09 GMT)
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Datacenter Watch: 2006-08-17
Aim to get all non-canonical URLs deindexed. What is left will be a mixture of normal and supplemental results. Let Google reindex the site. ...
www.webmasterworld.com/google/3051009.htm - Similar pages
Maintaining and Repairing Free/Busy Data
Messages that are duplicates of existing free/busy messages have non-canonical URLs because of the appended -x. Messages that have been upgraded or ...
www.microsoft.com/.../prodtechnol/exchange/guides/WorkingE2... - 8k - Cached - Similar pages

PHP Help: Apache 1.3 URL Rewriting Guide - Apache 1.3 Manual
Microsoft SQL - MSSQL · Flat File Databases ... Solution:: We do an external HTTP redirect for all non-canonical URLs to fix them in the location view of ...
www.phpfreaks.com/apache_manual/page/misc/rewriteguide.html - 107k - Cached - Similar pages