What I think Iyer means is that the discovery we all search for is not out in the world somewhere, but in ourselves. I know that I want to discover something about myself, and I know that once I find that long-lost part of me, I'll never be the same again, and I'll never see the world the same way again.
Iyer feels, as do I, that you can only really fully experience a trip when you live it. Tourists don't live trips; they go to the famous places, the historical buildings, and they see what the country wants them to see. What Iyer means is that to truly live during your trip, you need to make mistakes. You need to feel fear when you find yourself in a difficult situation that you have no idea how to get out of, and then you need to find a way out of it. Fear defines us, and it shows who we are in our finest moments or our darkest hour.
Yes, I do believe that travelers have a responsibility to share their knowledge and experience with all they visit and those they return to. A traveler, no matter how far he has traveled, has at least one story to tell, and it is unfair for him to withhold this information from his fellow people. However, I also believe that he should monitor himself, and not aggravate his listeners with careless or meaningless remarks about the dominance or power of his own country, compared to the lesser strength of the country he is residing in at the moment. Callousness is not appreciated.
"...I travel in large part in search of hardship--both my own, which I want to feel, and others', which I need to see." This quote is my favorite because I relate so well to it. I want to experience the places I go to, especially when it's difficult to be there, because I can overcome the obstacles and become that much wiser. And I need to see that I have so much, and am very blessed, while less fortunate people may not have as much. It puts my life into perspective.