“Black Hat” Search Engine Optimization is any method of trying to trick Google into giving high rankings.
Mostly this falls into two categories:
1. Showing Google something different than you show visitors to the site. This is called “cloaking” and there are many ways of doing so. Google knows all of them.
2. Setting up links to a site to make it look like the site is popular, when that isn’t really the case – for example by buying links.
It has long been known – and stated by Google – that these can lead to Google dropping your rankings drastically or even removing your site completely from its index.
Now a new video gives more information on this subject – as to when and how Google implements penalties (both automatically through its algorithms, and manually). And also how to escape from Google Hell.
The bottom line? It isn’t worth it (trying to trick Google in the first place)..