There are cons to nanotechnology. One of these cons is that jobs and employments will be lost at a very alarming rate since nanorobots can do a lot of work much faster and more efficiently as compared to a human. Another con is that the nanorobots are almost untraceable and could be used as a weapon of mass destruction. Or that this new technology will be very hard to make laws for and govern these rules. Here is a website for nanotechnology in medicine.