Noindex or canonical for duplicate mobile site?

[mcglynn]

We're launching a "mobile platform" version of one of our websites. Content will be duplicated from the main website, on the same domain, e.g.:
main - example.com/whatever/some-keywords.html
mobile - example.com/mobile/some-keywords.html

We want the top URL to be the one found by Google web search. But if users link to the mobile versions of pages, I'd love to benefit from that too.

The <link rel="canonical" ... /> tag seems like the right answer, but should we also put NOINDEX tags on the mobile versions of these pages?

I can imagine that NOINDEX might prevent the canonical tag from being used. But is the canonical tag sufficient to tell Google to index the main version rather than the "mobile" version of the page?

Is it possible that the page formatting or content is sufficiently different that Google might discard/ignore the Canonical tag and treat the mobile pages as new content?

[tedster]

I'd suggest using a mobile sitemap. Google is good (and getting better) at sorting out which url to show for mobile and which to show on a regular search.

Here's the support area at Google:
[url=http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=34627]About Mobile Sitemaps[/quote]