This penalty, that penalty, this filter, that filter - we now have a new one named the "-30 Penalty." But this one I think may have some substance. A WebmasterWorld thread has a lot of discussion on it, 6 pages, so far. Here are some quotes.
The report:
I just got my site rank #31 on its own domain name and bunch of keywords/phrases I usually watch were bumped from #1 to precisely #31. Those #2 through #10 are sort of all over the map but generally within the first 60 results.
WebmasterWorld admin Tedster said:
I've seen urls get a -30 and then seen that penalty removed in stages over several weeks after some condition was fixed. It sure looked automated to me. No, I can't prove that, except to say that Matt Cutts talked about wanting to do some automated penalties with automated removal quite a while ago. And in general, Google always looks to automate wherever they can because "it scales".
Donna suggests the cause of the penalty in this case:
I just looked at a site that someone on another forum posted the url for, which was hit by the minus thirty penalty. Turns out, that site would be what I would classify as a "thin affiliate". Does that ring any bells with any of your sites?
I think there are many things that can trigger this type of penalty. I have seen it also. I also believe it is automated.
Forum discussion at WebmasterWorld.
This entry was written the night before and scheduled to go live at the time below.

Comments:
Web 2.0
10/17/2006 06:28 am
This is the first that I have heard of this type of penalty. I would like to see some more studies with more proof.
Namish
10/18/2006 07:44 am
Its true google gives less importance to new sites.. However this -30 concept is new to me..
Judah
10/18/2006 09:00 pm
very scary....
Azhar iqbal
10/19/2006 05:43 am
Hugh! i am sick out here of these stupid filters... Now -30 penalty, it really threats isn't it?
Google Success
10/31/2006 11:20 am
Is this penalty the same as Page 4 penalty discussed in some other SEO forums? Looks like it is applied only to top ranking sites which do some black hat SEO.
Jonno
11/20/2006 09:24 am
I was also hit with this penalty. Hundreds of key terms formerly in the first few pages, relegated to #31. 80% of the site original content. 20% thin affiliate. That was 7 months ago. Immediately we removed all thin affiliate pages, submitted reinclusion requests. No response from Google. So we went through the site and cleaned up all html code so was a classic case of following webmaster guidelines. Trouble is once you are hit , that is it. Seems a manual inclusion is what is needed to get back in, but Google are not interested.
Jesse Brede
12/20/2006 04:06 am
My site was also hit by the Minus 30 Penalty but I managed to fix my problems and feel I've got a good grasp on the problem. I've started a blog to teach others the steps I took to resolve the issue. http://minus30.com
Jesse Brede
02/02/2007 02:39 am
To read more about the Google Minus 30, check out my blog.
No Name
06/24/2008 07:55 am
It's not a penalty, it's just dedicated to the webmaster who use too often "I don't know why"
John
04/14/2010 10:00 am
My site has just dropped from p2 to p5 for "quick hosue sale" keyword - have no idea why. No black hat. Rest of site - with other keywords - is still ok.
ray ban
09/10/2010 12:53 am
my site aslo happend this problem.damn it .
Fábián Gábor
10/22/2010 01:10 am
After trying a few alternative titles, Google Webmaster Tools is reporting me significant changes. For one of my most important keywords I moved forward 100 positions in about 3 weeks, which I consider a very great change. But for other, a bit less important keywords I'm getting backward.