Guest blogging has been a large topic over the past couple years in the SEO space.
In a recent video by Matt Cutts, Google's head of search spam, Matt answered the question:
How can I guest blog without it appearing as if I paid for links?
In that question, he showed overall examples of what makes bad guest blogging easy to spot and easy to find, in good examples.
Bad Guest Blogging includes writing off topic articles on a specific site and using keyword rich anchor text excessively.
Good guest blogging is when the content is written by an expert, the content has an bio at the bottom of the story and there is typically very little keyword dropping.
Matt added that the quantity of low quality guest blogging has been on the rise. He also suggested that if you do guest blogging, make sure to do it in moderation.
Forum discussion at Twitter.
Image credit to BigStockPhoto for target