An Interesting post on Search Engine Roundtable references the possibility that Google is using self page linking as a spam signal where Keyword rich anchor text is used. In case you are not sure what this means, let me explain.
Let’s say you have a site about blue widgets, and in your homepage content you have a link (or more than one link) pointing to the same page (homepage) with your main keyword set i.e. ‘blue widgets’.
So why use it as a signal, and what is this being based on? Well put simply, why would you link to the same page you are already on, if not to gain benefit that anchor text links bring. keep in mind that the anchor page also gets given more weight to its anchor text as well as the target page.
This has been brought up as a result of a thread on Webmasterworld forum, where a member states that out of their 150 sites, 3 got hit, and the only common element was this home page self linking. Seems weak if you ask me, simple but an effective signal. it could be enough to drop the trust on the page which in turn could impact on other elements.