If a site is caught attempting to manipulate the search results through cloaking, spam link building and other strategies that violate the Google webmaster guidelines then a punishment (penalty) may follow. This can take many forms from a reduction in search ranking position to an outright ban and removal from the Google Search Index.
If a marketer finds they have suddenly lost search traffic it’s a good idea to start by investigating whether the site has been removed from Google. This can be done by simply searching: site:yoursite.com. In the event of a ban you should fix any issues – your spam – then submit a request for re-inclusion on Webmaster tools.
If your site hasn’t been banned but is still suffering from reduced traffic it may simply be that some of your links have been disallowed or ignored by Google. There may be no need to take further action. However, if you find that some of your key terms and article headers that were often near the top of Google are now not even in the top ten or twenty results you may need to take similar steps as if you were banned – admit your mistakes to Google on webmaster tools and fix them up as best you can.