Every month or two Google updates it’s search algorithm. The latest update was on April 24, 2012 and it is called Google Penguin. This change was designed to avoid “spamming pages” which are pages that have little content, that are built in quantity merely to pass an anchor link, pages with keyword stuffing, pages with cloaking, and other bad quality sites, the list is long.
Of course if you have well designed web site, dully updated and follow Google’s webmaster rules, you have nothing to worry about. On the other hand, if you have been using “silver bullet” programs that for a fee promise riches and high rankings, you should be worried. Being honest and legitimate has it’s rewards.