What are the traits of bad links?

[PoolMaster]

What are the traits of bad links?

[Pihu]

As long as you can avoid these seven characteristics, all of which can make a link “bad,” you'll remain in good standing.

[rscomponentseo]

It's On A Low-Authority Or Questionable Domain. ...
It's Pointing To A Source Irrelevant To Its Content. ...
It's Repeated Too Many Times On The Domain. ...
It's A Part Of A Reciprocal Exchange.

[Neo_5678]

Bad links traits:

1. It’s On A Low-Authority Or Questionable Domain
2. It’s Pointing To A Source Irrelevant To Its Content
3. It’s Repeated Too Many Times On The Domain
4. It’s A Part Of A Reciprocal Exchange
5. It’s Embedded In Suspiciously Keyword-Matched Anchor Text
6. It’s Isolated From Any Meaningful Content
7. It’s A Part Of A Scheme

[Lukedawn]

It's On A Low-Authority Or Questionable Domain and pointing to a source Irrelevant to its content.

[amarnathsmm]

Link Farms
Website Forums
Chatrooms
Article Directories
Paid Sources

[yuva12]

Links from sites that are unrelated to your sites
Low authority domain
Links from low Page Rank and Low traffic
Links from link exchanges