I think limiting the trades to knives would make it much more difficult to work your way up, and require you to know a huge amount about the market value of all sorts of knives. With all knives, I think people will tend to value them in a similar manner, as opposed to an open market where anything can be traded. Not impossible, just more time consuming.
I looked at the sequence of trades the guy made, and several of them seem like the sorts of things people would donate or throw away, meaning that they don't hold much value in them. I mean, who would trade a coleman stove and fuel for a doorknob? Also, the amount of publicity this guy got helped him quite a bit. When asked if there was anywhere he would not go, he said Yahk, BC. And then the next day he was offered a trip to Yahk for his snowmobile.
Personally, if I was just being offered this trade and not involved in the crusade that this guy was, I would keep the snowmobile.
I think that moving from a paperclip to a house in 14 trades is only something that will happen once. Like the person who made a million dollars by selling a million pixels of advertising space on his website for a dollar a piece. Its all publicity.
I'm not saying that you couldn't trade up quite high if you know what your doing, but without the publicity it would just be a lot harder and require more trades.