If your site has been penalized by Penguin or Panda, or if you have received a manual penalty, your first instinct is probably to try and help the site recover in rankings (provided that you weren’t already expecting this and gave up on the site in advance). Even if your site was penalized for having a multitude of harmful links pointing to it, recovering it may still be an option, but it may also be a resource and time sink that will ultimately result in failure. Knowing whether it is feasible to attempt recovery can be quite difficult, especially since people can get emotionally attached to their sites, but giving up on it can sometimes be the only reasonable option that you have left.