I'm very interested in the outcome of this as I am building a service similar to Padmapper in the sense that it uses data from other sources to make a better user experience for people, and I'd love to include Craigslist (Would be a big supplier of data for my users), but I don't want to deal with these types of things so I have been leaving it out.
I think the key thing here is that you have to talk to your data sources. You have to use their data source the way they want you to, or come to some sort of agreement (licensing or somesuch), else you are moving into the same legal territory Padmapper was in and risk getting sued.
