Anyone need a snowmobile?
This rules. Kyle MacDonald started in Canada with one red paperclip with the goal of trading it for a house. He's willing to take several steps, of course. So far he has "traded up" for something better six times and now has a snowmobile! There are so far dozens of offers for the snowmobile including several cars and various other cool items.

I imagine this is going to get a lot harder the closer he gets to his goal. His story is really cool and people would be inclined to participate with small-value items just to be part of it. Trading a fish pen for his paperclip is cool enough to do even if you happen to value a fish pen more highly than a paperclip. People will be less inclined to casually trade down to a snowmobile just for kicks.

Also, in general, the more valuable the items become the more fixed the market value is likely to become. Fish pens and even neon Budweiser signs gain a lot of their value from presence in a particular place and tickling widely variant fancies. Snowmobiles likely have a fairly liquid market in Canada and thus people are likely to know exactly what they are worth. It'll be fascinating to see if he can overcome this. Granted the snowmobile in question was previously owned by a minorly famous person, which could help.

I think that the only way he will make it is by sticking to things that have a wide distribution of valuations in the market. A painting might be a better choice than an ounce of gold because trading up might be possible by finding someone placing an extremely high value on the painting. Of course, people who are good at exploiting such markets are typically in the business of doing so. It's hard.

I wish Kyle the best of luck. I wish I needed a snowmobile. :-)