From an interview with ex-Googler Kaspar Szymanski:
But the first and foremost, the most important thing to clarify—because this is a very common misconception—is the fact that there is no such thing as an algorithmic penalty.
There are algorithms and manual penalties. Those can have a rather similar impact. They can feel like they are the same thing, but it is very important to understand that they are very different in the way they need to be handled.
If you are interested in the details of manual penalties (or web spam actions as they are usually referred to) then the full interview will be of interest.
