It is mutual and that's why most of the webmaster are complaining, whining and crying all over the place.
Not all webmasters, some lost their top spots, others that didn't have them previously now have them and are raking in the cash lost by the whiners. You probably won't hear much from the Panda winners because they don't want the whiners to focus on them and try to unseat their new found gains. They'll quietly rake in the dough, work hard to maximize it while they can, while others waste time complaining and not getting back to business.
Reality cramps are that only 10 sites can be at the top 10 and if one webmaster isn't there, another one is, and you only hear from the guy that lost his free ride. It's unrealistic to expect to keep that top 10 spot as everyone is gunning for your spot already. Truth is, most will never really know if it was a competitor, Panda, or a perfect storm of both that unseated them in the latest updates.
Like others have rightly said, if you only rely on Google free traffic as your only source of traffic then you have a loser business model in the first place. I've lost Google before and I didn't disappear off the map thanks to the fact that I get direct traffic from links on other sites, bookmarks, Yahoo, Bing, social media, and a wide variety of other free traffic sources. Webmasters that don't cultivate those traffic models don't have a real business, they don't have a sustainable business model, and will ultimately fail.
Yes, I get links to drive traffic to my site, not raise my PR in Google.
Many webmasters have forgotten this age off source of traffic, too bad for them.
If your livelihood is tied solely to Google SERPs and AdSense, the odds are more likely than not one morning you'll wake up and you'll be screwed.
With respect however, your post sounds like something I would read on the official Google webmaster forums. Those that understand that mentality there would applaud your sediment.
With respect, that's just insulting.
The OP decided to sell his site and get out, that's better than waiting for it to fade further and with full disclosure he was lucky to find a buyer IMO.
I've been on the Google free ride for years as well and got semi-trapped in Panda but since I have an actual business model that uses more traffic sources other than Google SERPs, I'm still up and running making money.
Do I make as much post-Panda? Nope.
Am I dead in the water? Nope.
Still making money and still milking this cow as hard as possible.
I didn't decide to sell my site but decided to take some of the technology from my site and start selling it as an online service. The upside to selling online services is the swings of Google SERPs don't really have any impact as traffic won't be my focus, it will be on customers who will already be using the service.
See? A business plan.