It happens, but if you've already tried to remove the penalty yourself you know it's virtually impossible to succeed.
Google makes it sound so easy to do a Penguin Penalty recovery....
But what they don't tell you is that it's really a HUGE undertaking requiring weeks and weeks of time, sometimes lot's of cash, and a team of people with specialized knowledge of exactly what Google wants in order for them to lift the penalty.
The bottom line is you're site is struggling, your old rankings are toast, you can't rank your site for new terms, and your revenues are down your business is in trouble. Now what?!