I think where you and I differ is that I don't believe that people who use Craigslist are under the impression that their data will be indexed/used elsewhere; I know I've never assumed that, and I'm willing to bet the same goes for the every day person. If I post something on CL, then I expect others to find my ad through CL. There's almost this unwritten social contract that users expect services they use to participate in when they submit their data.
But the more I think about it, I do see that it's not as clear-cut as I previously thought. There are tons of sites that store and display our tweets without our explicit consent, and we, at least I, seem to be ok with that.
If it makes you feel better, PadMapper is attempting to act in a way consistent with search engines - give a bit of a preview of a listing and then link back to the original. It's not taking the text and reposting it or anything like that.
I think this is a bit disingenious. Google indexes the entire web, not just a specific subset of it that it can hopefully in the future turn a profit by supplanting Craigslist (ie links and leads to Padlister). This is why you see CL allowing Google to index their website. If CL thought Google was going to spin up apartments.google.com relying off the back of CLs data you could probably expect a lawsuit there also. It's all about context and to suggest otherwise is just trying to find a way to profit off the back of another company who has already done the legwork.
But the more I think about it, I do see that it's not as clear-cut as I previously thought. There are tons of sites that store and display our tweets without our explicit consent, and we, at least I, seem to be ok with that.