How to know if your site has just been penalized by Google Search? It's easy, if you lose a lot of traffic from one day to the next you know it comes from Google because unfortunately Google has the biggest market share in the search engine world..
So just look at the web tracking statistics from Best-Reviewer.com and you'll see how obvious it is from 21st august with the common 3,000 unique visitors per day to less than 1,000 the day after.. And the day after..
If you look more closely at the incoming traffic you'll see still some visits from Google, but if in the last 50 visitors you see a lot of visits from Bing and Yahoo, you know you have a problem..
Why do you get a penalty, this is totally unknown, there is no message in the google webmaster tool (I've checked and it says "No new messages or recent critical issues.") and you're left wondering why now and why so suddenly..
Unfortunately there's nothing you can do except freaking out, posting on SEO forums and such and that's not positive, constructive, a total waste of time, so you can only hope that Google will start sending more visitors as suddenly as they started sending less. Plus as you know Google was already capping its traffic, because it is not possible that with a lot of new content posted by more and more members should result in the traffic being basically the same daily for months on end..
So, here you have it, Best-Reviewer.com has been penalized by Google for whatever reason, we can speculate about it or we can just move on and invest our time on things we have control over and not on some anonymous, unreachable virtual entity :-)
Eventually the traffic will come back, maybe it will take one week or one month, but I've had the case before on other sites, sometimes it happens and we don't know why.. And honestly should we care? If they're not ready to tell us in other ways than vague terms, then we should not waste our time with trying to reverse engineer their algorythm, because honestly there's no way to do it correctly and don't we have better things to do with our limited time on earth?
But I posted this message so you know that if the same happens to you on your site or blog, don't worry about it, the traffic will come back eventually, or not, but you should invest your time into trying to make things that don't rely too much on Google, as I've learned it after 9 years with adsense and a sudden kicking out of their program with no clear reason given.. That put me back in place with reality and how they value our efforts / collaboration.. It's like an egoist spoiled kid, you can't really blame them for being like that, or teach them better, it's not our job, better to just move on and ignore them..