I do not understand your tread... I guest that you have 5 blogs ( 5 domians ) and you post to 5 blog in 1 niches.( the same niches)--- it is no good or you have 1 blog and you post 5 different niches, if you do this, it is the best.
Yes. And a ridiculous waste of time and energy. Create a blog that people actually want to read, and they'll link to and post your RSS feed across the web for you.
Eventually the four out of 5 blogs you have will be punished for duplicate content. The only one who is not likely to be punished is the one in which the story originally appear