If anyone is the party we should feel bad for in this case it's 3Taps. They seemed to be flying under the radar until Padmapper started using them.
But craiggers provides a very valuable service, namely showing pictures of items as you search. It made furniture searching so much easier.
I have zero sympathy for craigslist. They didn't get into their position through "years of hard work". They won the lottery (someone had to win it). They have done zero innovation (other than maybe anti-spam) for years and prevent others from innovating on top. Society wins if they are forced to open their data.
Name one startup that began knowing they were going to be sued and went on to a successful exit.
Parenthetically, the original Napster, the one that began knowing it would be sued, was sold about 3 years after its founding for less than $2.5 million as part of bankruptcy proceedings -- and I doubt that the owners took any significant dividends out of its before its sale: http://en.wikipedia.org/wiki/Napster#Current_status
Some do it to prove a point, some do it to prove that the market exists.