Off page anchor text (the text in links to your site from other sources) is one of the biggest components used by search engine ranking algorithms. You should ensure that, wherever possible, inbound links point to pages on your site with the appropriate keywords contained within your anchor text. Of course you cannot fully control the inbound link anchor text but you can keep a close eye on back links into your site using Google Web Master Tools or backlinkwatch.com.
If you are currently taking part in (or planning) a link building campaign you should ensure that your back-link portfolio is looking natural. You should be looking at having 50% – 80% of your back-links using keyword rich anchor text relevant to the page you are linking to but remember, overusing specific keyword phrases can result in a penalty from search engines if you suddenly begin to amount large numbers of inbound links. Try to mirror you historical link growth rate and do not assemble to many inbound links in short space of time.
Keyword rich anchor text is only of the many simple techniques for search engine optimization (SEO) at your disposal.