"Hangs itself" seems overly dramatic. Given the time-sensitive nature of many Craigslist, it's likely that most of Craigslist traffic comes from people using the Craigslist search. Others may object to Craiglist protecting their data because it stops them from creating value-add businesses on top of it, but few complain of the high cost of the Twitter firehose.

If the data has value, it's perfectly reasonable for the owner to charge for access. And Craiglist owns the data, as their T&Cs make clear.