Here's what Google themselves have to say on the matter:
You can perform a Google search using the link: operator to find a sampling of links to any site. For instance, [link:www.google.com] will list web pages that have links pointing to the Google home page. Note there can be no space between the "link:" and the web page URL.
To see a much larger sampling of links to any verified site in Webmaster Tools:
Note: Not all links to your site may be listed. This is normal.
- On the Webmaster Tools Home page, click the site you want.
- Under Your site on the web, click Links to your site.
Here's what Matt Cutts (head of Google's Web-spam team) had to say in a video on the subject:
The short answer is that historically, we only had room for a very small percentage of back-links because web search was the main part and we didn't have a ton of servers for link colon queries and so, we have doubled or increased the amount of back-links that we show over time for link colon, but it is still a sub-sample. It's a relatively small percentage. And I think that that's a pretty good balance, because if you just automatically show a ton of back-links for any website then spammers or competitors can use that to try to reverse engineer someone's rankings.
Google themselves is telling us not to pay too much attention to the link command, but that doesn't seem to be stopping folks. Let the myth busting commence.
