Tommybs - 10:39 am on Nov 1, 2010 (gmt 0)
In theory anyone can post a link on their feed to your site, but it still might help you to put a like button on your site, possibly with the added comment functionality - encourage them to share rather than just hope they do. Facebook 'weighs' people's likes etc. to give them prominence in the feed and I think if their also writing comments it might give them more weight, and the more you get the more they might see it as important. The links are mainly just that, a simple link, however they do appear in searches on Facebook I believe.