Definitions. This is the modern infatuation with joining other bloggers to boost your coverage.
Who benefits? From my experiences, the only person who benefits is the person paying for the set up.
My experiences. These vary through people not giving me information to post, to help them. To people not saying thank you for the help. To finally, people being plain rude, and expecting you to do them a favour without even asking you.
On blogs. Over the last three years, there have been two constants to my writing for other peoples blogs. 1) Everybody has said my posts increased their blog readers enormously.
2) I saw no feedback to my blog, despite helping others.
Changing views. In the beginning, I was eager to help others, but over time the one-way system turned me off. It has nothing to do with SEO, or any other rubbish you want to name it. The bottom line reads the same. I helped people, and got no help in return. These days, I will do as little as I can to help people outside of those who I feel helped me, or our charity The Peacock Writers.