This word of caution most frequently applies to affiliate sites whose republishing of product descriptions,
images has come under search engine fire numerous times.
In fact, it is best to anticipate manual evaluations here even if you have dodged the algorithmic sweep.
The basic tenets are:
- Do not simply republish something that is found elsewhere on the Web unless your site adds substantive value to users,
and do not infringe on the copyrights or trademarks of others.
- If you are hosting affiliate content, expect to be judged more harshly than others, as affiliates in the SERPs are one of users' top complaints about search engines.
- Small changes such as a few comments, a clever sorting algorithm or automated tags, filtering, a line or two of text, simple mashups, or advertising do not constitute substantive value.