The document returned is "low quality".
That's one of the main reasons people get flagged nowadays. If your website is just crap and it's just online because of advertisements or other shit, then Google will get you... maybe not now but in the future they will.. just stop making crap start making great websites with great information.
A lot of SEO'ers think like this nowadays:
Ok, we take a exact term URL and link build it as fast as possible...We wanna go to the top with many keywords in a short time..
The reasons why they fail is just because you should look at the long term:
Make a beautiful website, create a good inner structure, take some time for it.. implement a good article everyday (15 minutes every night).. start building some links and the society will do the rest.. in the end you will have success.
If i visit a company and they ask me... can you get me as fast as possible in the top10? I tell them: WRONG! You need to build quality! Because you wanna build a great business! Do you want to pay a lot of money for 4 months success? Or do you wanna build up a great business and go for the long term success?