An official post earlier today on the Google Webmaster Central Blog announced that users of Google Sitemaps will now get a much more detailed view of the number and classifications of inbound links to their site.
Google’s link: command provides a mere snapshot of the total number of inbound links to any site. The Webmaster Central tool offers a much more comprehensive view of the external and internal links to a domain and to individual pages within the site.
This will still not be 100% of the links to a page, though no explaination is provided about why Google don’t actually provide the exact link numbers.
Read the full post about Who Links To Your Site.