tedster - 1:23 pm on May 16, 2011 (gmt 0)
To be more precise, several Google spokespeople have said that Google takes the canonical link as a strong suggestion. They do reserve the right to ignore it, however, that is not what commonly happens even when there is a hack or an error.
For more discussion about this area, see the discussion Why Are There "Canonical Disasters" - Is Google Messing Up? [webmasterworld.com]