Market failure

The law of unintended consequences doesn't only afflict government actions.

Craigslist springs up to facilitate low cost transactions between individuals:  good!

The market for used furniture booms, allowing people to furnish their houses more nicely/cheaply, while giving a little extra cash to those parting with unwanted furnishings:  good!

The boom in used furnitures spreads bedbugs, leading to a quasi-epidemic in some areas:  eeeeeeeeeeeeeek!

Now I'm afraid to buy any used furniture at all, other than from an antique dealer.  (Which means, I'm not buying any used furniture).  As far as I can tell, the only real way to get rid of a bedbug infestation is to throw out practically everything you own.  It's not worth saving a couple of hundred dollars on a futon if it means I might have to throw out thousands of dollars worth of other furniture.

When markets fail, we're supposed to recommend government intervention, but damned if I can think of one that would solve this problem.  I think we're stuck with Caveat Emptor.