You just found this line "Google has several ranking filters. We know of a -20 or -25 filter, -100 filter, and the -950. Yahoo! does the same thing, but different filter ranges." in a blog comment and decided to start a discussion about it, didn't you..
About nothing actually. This is like trying to discuss wether or not a fire made in afrika resulted in a specific rain cloude over oklahoma. "were you affected by that 10 hour fire that was made in afrika?"
Somebody says: "hey my site dropped from 2 to 6" and some other people heard that and say: "Oh mine too". Yeah that probably means Google did something.
-5 filter? Then why a drop from 2 to 6? That's 4 positions.