A WebmasterWorld thread has one webmaster who runs about 150 web sites. Three of those web sites noticed a ranking decline in Google around the same time. He said, the only common factor amongst those three sites and not the other 147 sites were how they used anchor text on the home page to link to the home page.
The webmaster said he believes those sites were penalized because they use generic anchor text on the home page, pointing to the home page, for the site's topic.
The webmaster wrote:
Of the 150 of so i am managing currently, 3 were hit a couple of months ago, and the only thing i can see in common is they all have a home page link on their main keyword to home.
Cats - anchor text to home page.
Window cleaning - anchor text to home page.
Many agree that this can cause the home page to not rank for the keyword being targeted in the anchor text being used internally.
To me, it sounds a bit strange and too simple. But hey, most of the webmasters agree with this.
Forum discussion at WebmasterWorld.