To Interact or Not?

Great question from my cousin:

I'm sure you saw the pictures this week of a tribe in the Amazon that has had NO contact with the outside world. To intervene or not to intervene...that is my question. Do you leave these people alone, or go in and say hello, maybe offer them a coca-cola? My initial response is to leave them alone, but what if their average lifespan is 40? What if many of their children die of preventable diseases? What if they often go hungry? What if they are bored and would really like an ipod?? What if they haven't heard about Jesus?

Well? We certainly seem to have the reverse Midas touch when it comes to interacting with other cultures. At the same time, certainly there are some things we have to offer. Interact or not?