Market Inefficiency in Sea Kayaks
You can exploit inefficiency in non-equity markets, of course. Here is a way to get screaming bargains on used kayaks from craigslist.
The result is effective, but potentially creepy: you post an item on Craigslist, and your phone rings 5 minutes later with my offer to buy. This freaks a few people out.
Using this method, I bought a nearly new $1500 sea kayak for $600, and a well-maintained $1200 Stairmaster for $200. Beneficial deflation in action.
(You could do this with an RSS reader, as craigslist can publish your search as a feed. But I always forget to check RSS. By contrast, nothing shakes you by the lapels like an incoming email saying, “bargain here.”)