I see it all the time in the SEO forums -- Google slapped some sites around, and site owners are making much less money from those sites than they used to.  There are thousands of posts about this topic, white hat sites being banned, black hat sites ranking well, gray hat, blue hat, it goes on and on -- all the crying, whining, and complaining could fuel a small country with the heat being generated.

I've been there myself, so I understand the frustration of these webmasters -- it's hard to focus on moving forward when you've just been slapped backward without warning.  The best thing to do is to bear down and keep building new sites and new content -- focus on the future, not the past.   The more content you write, the more products you create, and the more sites you can get up will help you get through an unexpected delisting or rank decrease a little smoother.  Those multiple earnings pathways help even out the bumps in the road, so stop feeling sorry for yourself and get to work.