There's other penalties like the -50 and -950 penalty.
Here is strange coincidence.
I entered to this last contest and on the same begining I took the 6th place, then I asked friend for backlinks and I did not expected they will all react so fast, so in two days I managed to get maybe 10k signature links.
Soon after that site dropped for exactly 30 position from 6 to 36 and after that its cruisiing from places 32 to 39.
Sound to similar.
Now I am thinking what to do, I never experienced any penalty neither ever happened that I got so big response from people around me with backlinks.
I am on unknown teritory, to stop link building and concentrate on adding content? Or to keep my rates ignoring what happened?