I also found this: "The penalty also seems to affect web pages that are listed with an appealing title and a description that is very relevant to the search term so it might be that the click-rate is not taken into account. We think that it's more likely that the word and phrase relationships are the reason for the ranking drops. It seems that web pages with too many inbound links using exactly the searched keyword as the anchor text were affected by the filter. If the link to a special web page always uses exactly the same anchor text then the word variety is probably extremely low compared to the competing websites in the top results. That indicates a manipulation of the anchor texts and Google applies the filter."
Well, you'd have to be an extremely stupid SEO to buy 1000's of links on different websites all of them having the exact same link-text. Yes - I would not be surprised if after a certain number the text no longer ads weight, but I would also be surprised if it suddenly weighs against the site the link points to. It's not so much stupid because there might be a google penalty - I don't think there is one - but because it is not likely you only want to target those specific keywords/phrases and not others.