Findings collected from Google "sample links" for penalized sites
It's an interesting recap here. Before going indepth, mind this part:
Now to the findings from 34 bad link examples:
* 29 links => exact match keyword anchor text (this one is obvious).
* 1 => comment spam with the client’s brand name (!). This one should be specific to manual penalties
* 1 => an author of an article as anchor text, but it was scraped or copied by a 3rd party. This one is weird: If the reviewer was human, why didn't he/she realize that was a scraper?
* 1 => client homepage URL, but it was essentially bookmark site spam.
* 1 => related to PR submission (Didn't Google say PR links won't cause a penalty and will be just discounted???).
* 1 => partial match keyword anchor text (!). But mind the comment below:
Some of conclusions are obvious as well but these should be taken note of:
- Bookmark sites are not safe (I see many people at SEOchat who claim to be still doing "bookmarking to gain natural links" ;))
- Don’t like comment links that are either used in excess or do not offer a name for the person responsible for that comment. (please mind Matt's vague note that nofollow links in the comments can still trigger penalty http://www.threadwatch.org/node/21182)
Everything will be ok in the end
If it's not ok, it's not the end