I've often wondered about the demand side of bike theft, as in where all the stolen bikes go. I'm still searching for a plausible explanation for where the bikes go that accounts for the facts that (a) bikes of any and all values are vulnerable to theft (b) the theives take a considerable risk by actually doing the theft, (c) the thieves are highly proficient and (d) in many places, bike theft is rampant.
Around here at least, there is no established market in used bikes. Bike stores generally don't bother, so it's mostly person-to-person sales through Craigslist or ebay. It's hard to imagine that anyone could move enough bikes that way for it to be worth their while.