AutoBlogging software is as legal as P2P software...in other words, completely and totally legal. Where the illegality of it comes in, is with it's use.
Use P2P software to download copyrighted content, and you're breaking the law. Use it to download a movie your sister made on her camera that she wants to share with people across the globe...perfectly legal.
Use autoblog software that is only grabbing content that is legal to re-print elsewhere, perfectly legal. Use autoblog software that is grabbing content that is copyrighted and not legal for re-print/re-distrubition elsewhere...illegal.
In other words, autoblog software is inherently legal in and of itself. The legality of it comes in with it's use (and even then, it isn't the software that broke the law, it is the user).