This question is, of course, remarkably late - many moons after Google started supporting the cross-domain canonical link element. But in light of all of the canonical-related questions that have been popping up in this forum, I thought I'd ask. If there are two sites with pages containing the exact same page of content - let's say a news syndication site and the original site containing the article - and both of them have a canonical link pointing to themselves, how does Google determine which one should be indexed/rank first? I've seen a lot of noise re: the Mayday update and this specific issue as well, this seems to be the major SEO issue of 2010.