Why is it that a cached site, say on google, with a link to your site doesn't appear when you do a link:yoursite.com search of your site?
Google have always said they show a sampling of links "To find a sampling of pages that link to a URL (for example, www.stanford.edu), go to the Google Advanced Search page at http://www.google.com/advanced_search and enter the URL in question into the "Links" search box. Alternatively, you can perform a link search directly from the Google search box by typing [ link:Stanford.edu ] or [ link:www.Stanford.edu ]. There should be no space between "link:" and the URL. To obtain a comprehensive list of sites that point to a page, perform a Google search on the URL. From the search results page, select the "Find web pages that contain the term" link, and Google will provide you with webpages that mention that address. Note that in this case, Google will return all pages that mention this URL, not just those that link to it." http://www.google.com/support/webmasters/bin/answer.py?answer=34453
Use Google Webmasters Central to view all your external backlinks that Google has found. This is the best way to view them all and you can download them via a CSV file and see when they were last found.