People haven't just thought about it, people have done it.
Matador has an article on it, and here is a guy that did it for
400 days. Somewhere I came across a site of a guy who was travelling continuously without any cash.
I have personally met some people travelling on what I consider ridiculous budgets. I met a guy in Costa Rica who was trying to do $US 10 a day on average. he was camping, mostly, and had a fishing rod to catch his own dinner. I met him in Montezuma. He ended up trading a fish he caught with a camp ground owner in exchange for 5 days free camping, saving himself $10 ($2 a night camping fee, I believe).
Of course, with miles and points I have had a few trips where my only expense was taxes on the rewards tickets and food and beverage, but that probably isn't exactly the same thing.
