As others have pointed out Craigslist can claim copyright to the collection. The legal theory I would expect them to use is that PadMapper wouldn't know about these listings if they didn't access Craigslist's collection, therefore their use of the collection violated Craigslist's copyright.
I did a quick Blekko for the case with the Yellow Pages that was litigated this way (but alas did not find it) where a AT&T sued the maker of a competitive Yellow Pages over using the collection of businesses in their book. The defendant argument was similar to yours, that they could have walked down the street and collected the information so the information wasn't copyrightable, but the judge ruled in favor of AT&T because it was clear the defendant could have done that but they didn't do that. There was some errors and omissions that mirrored the Yellow pages and 'proved' the defendant took their data from the Yellow Pages rather than collect it themselves.
For PadMapper to escape liability they have to be able to prove they came to know about these listings in some other way than through Craigslist's collection of them. They argued in their blog that 3Taps did that for them because they got them from 3Taps they aren't liable for what ever 3Taps is doing. And my take on it is that given the case law it will be a very hard thing to prove. If Eric Goldman is reading he could probably whip out a definitive argument here.
If it goes to trial I'll definitely follow the case to see how it plays out.
In Feist Publications v. Rural Telephone Service Co, a phone directory was ruled to be protected by copyright only if the selection and arrangement of facts was an original creative act (listing numbers alphabetically was not).
I'm aware of a case after Feist where a yellow pages for chinese immigrants was copyrightable because of the creativity involved in selection of the facts and the arrangement into categories. But even then the facts themselves are not copyrightable.
Craigslist's selection is nonexistent, you send it they publish it. And the arrangement of the subset that padmapper is using is solely by geographic location and time. In addition padmapper is not copying the arrangement.
I did a quick Blekko for the case with the Yellow Pages that was litigated this way (but alas did not find it) where a AT&T sued the maker of a competitive Yellow Pages over using the collection of businesses in their book. The defendant argument was similar to yours, that they could have walked down the street and collected the information so the information wasn't copyrightable, but the judge ruled in favor of AT&T because it was clear the defendant could have done that but they didn't do that. There was some errors and omissions that mirrored the Yellow pages and 'proved' the defendant took their data from the Yellow Pages rather than collect it themselves.
For PadMapper to escape liability they have to be able to prove they came to know about these listings in some other way than through Craigslist's collection of them. They argued in their blog that 3Taps did that for them because they got them from 3Taps they aren't liable for what ever 3Taps is doing. And my take on it is that given the case law it will be a very hard thing to prove. If Eric Goldman is reading he could probably whip out a definitive argument here.
If it goes to trial I'll definitely follow the case to see how it plays out.