I recently happened to read in reputed forums and blogs that acquiring links with ‘exact match anchor texts’ is considering as spam. Google devalues exact match anchors from its algorithm. Doing that leads to a drop in the position of your website for anchor text. You can read more on the subject on seomoz beyond exact match anchor text. Another good article from Search Engine Journal on exact match is Searchenginejournalexact match domains. I have realized that after Penguin Updates many websites fell in rankings because they used exact match anchor texts.
It all means that you really need to use anchor text variations for back links. Never use exact anchor text which is your targeted keyword. For instance, if we run a website for SEO Services and you target the same, you can vary the anchor text as Web Promotion Services by Search Eccentric and Search Engine Optimization Services from Search Eccentric etc. It should look natural and not spam.
GUYS DON’T WORK FOR SEARCH ENGINES BUT FOR USERS!!!