There are loads of sites offering to automatically send content to my blog for free. I see what they get out of it (backlinks) but what do I get? Surely this new content is of no use as it is no doubt going to dozens of other blogs at the same time. Therefore google are not likely to index the pages for my site or maybe it will even harm me. I certainly won't get any credit for this content that has been published elsewhere but I will be seen to be linking out to other sites which could be bad for me.
Am I missing something? Why are so many people signing up to these things? How will this benefit my site for SEO?