Total penalization or banning is easy to spot. You disappear from the index. Period. Partial penalization is a real problem for any SEO or webmaster. I noticed that some of my managed domains perform better than others, and I am collecting indicators for Google duplication/bad content penalization. So far, the only way to tell if a domain underperforms due to penalization is to run an experiment. For those experiments, I use similar pages under uncommon keywords. Does anyone have any accepted indicator for penalization?
Here is a quick one for sites that have been around for a while (a couple of years). If you type in "site.com" and you are not listed on the first page (top 5 at least), it may be a sign of a penalty. I have seen this penalty on one of my sites but a Google reinclusion lifted the penalty.
I've heard others say that if the problem was fixed, the penalty would be lifted, but others saying that you must submit for reinclusion. Does anyone have past experience with the penalty being automatically lifted, without reinclusion request?
I have a site established in 2000 with 14 dmoz listings. We had an affiliate shopping section with manufactuer bios that were dupe content. This was fine for at least 2 years. Our rankings dropped on our content pages dropped one day, and never really regained rankings. After a year of this, I took down the affiliate section. 2 months later, our content was ranking well again. Lesson learned.. be more than paranoid when it comes to duplicate content.
Google's dupe content filter seems to be screwed loose on this last update. Not doing well at finding the original publisher. Will wait for the next and see if things come back to normal.