Have humans gone too far with this?

I am not a big fan of screwing with nature. As long as they don't create lots of something higher than us on the food chain. but i am For the cloning of Mammoths - our species made them extinct, it is only fair we help them back. Cloning is being used to help other species not yet extinct - like the Barbary Lion. As long as we dont get carried away and we start cloning deadly animals we can't control.