Is nano material really safe?

I am sure you have heard of lots of interesting and promising nanotechnology products - shirt that repels water; minute particles that detect cancer cells or deliver drug to the cancer cells and not harming the surrounding normal cells. I too, believe that this field will be 'big'. However I can't help but feeling rather 'insecure' with the 'super small particle'. Is it really safe to human being? Would it one day 'back-fire' us? then I saw this article : Carbon nanotubes: the new asbestos? - report on nanotubes cause precancerous growths in mice. My heart sank.
Even though there is no conclusive finding but it is possible. I guess may be it is a good thing that they found out now than later. Hopefully the experts in the field will design a better way in making a safe nanotube and also to have regulation to ensure that it will not turn into another 'asbestos'.