gn_wendy - 7:09 am on Aug 19, 2010 (gmt 0)
My two cents:
I am not a big fan of the canonical tag. I have not, until recently, advised a client to use it.
The case where it makes perfect sense:
The client wanted a forum on their page. They have had this for a long time, but it was outside of the indexable content. Finally they have consented to letting it be indexed. They are using an open source platform and are not willing to fix certain issues. Each thread has a canonical for each reply in that thread.
Implementing the canonical tag was the only thing that made any sense at all, because they have no resources to fix the real issues.
The index was a real mess. Since we placed the tags, everything is peachy and the linkjuice is flowing as it should.