From the article: "2) reducing the aggressiveness of our SEO, which reduces total traffic in the near term but increases the relevancy of Scribd links in search engine results"

The real question is whether or not they got Google smacked before making the changes.

Dare I ask how Scribed got to a point where their SEO is too well done?

Super high page rank + lots of pirated content + well optimized site. I think that's it.

That, and, if I am not mistaken, incorporating search terms of previous visitors into the page. Somebody would search for 'iPhone widgets' in Google, click on the Scribd link about totally unrelated'wooden widgets', and Scribd would put 'iPhone' on the page, making it much more likely for the next person to be misdirected.

the word they ad are invisible or visible? If visible where do they put it? in tags? description?

Come on dude... they did change their tactics, is what the article says.

possibly you should blame Google if you don't like the search results, not Scribd...

Well, its like saying that you should sue the police when your house got robbed instead of the robber. Scribd is the one with the intent of gaming the system, Google just wants to provide relevant search results, so its clear to me who should shoulder the blame.

no, its not clear at all, the failing is with Google for preventing what you call "gaming the system", and your analogy is flawed for the same reason. Using your analogy lets say you hire a security firm to protect your most valuable asset, then you get robbed. Who would you blame? Clearly the answer is a function of both.

However, I'm not even convinced of that Scribd have managed to game anything. Can you provide a link to google search results that backs up your claim?