Till now computers were being used only to automate human manual and laborious work. We are already seeing positive and negative effects of it - positive in the sense that we are more efficient and more capable to save everybody from disease/crimes etc. Negative for few whose job is taken away. That looks fine as long as there are new jobs being created.
But now in the new field Artificial Intelligence - human brain is being replaced by computer. And I can see that day is not far when a single human would be so powerful that he/she would be able to take control of(enslave) entire human race alone with help of added brain given to him/her by artificial intelligence. Even army is investing there - http://robobrain.me/#/about
Please at least keep track of all possible negative influence too