Google recently released a System update to their search engine algorithm. In fact, they released a few updates in past months. First there was an update which required you to place ads above the fold on your website when viewed in your internet browser. Next came the Google Panda update which many people were not affected by. This update was released upon the internet and targeted low quality sites. Many webmasters lost rankings in blog networks, articles networks and link farms. This was mainly due to poor content and spun, unreadable content.
The latest update which caused a huge disruption to the webmaster world is codename Google Penguin released in April 2012. This update is targeted at unnatural backllinking methods, spammy content, unoriginal content or duplicate content and link schemes. Now, this does NOT mean you have to stop building them. However, you should be more careful in the ways you go about obtaining them.
The key is to STOP building spammy "anchor text" focused links. I DO NOT recommend automatic article spinning or automatic link wheel building. This MUST all be done manually or you may be faced with penalties. Play by the rules and you will reap the benefits. Plus, do NOT focus solely on building "anchor text" links. You must diversify by including your site name as the anchor.