My understanding was that, as the owner of a site, (even one that hosts mostly/completely content created by someone else), you get to dictate the terms on which any party accesses that site. It would be like if YouTube said that you may not access their site with anything but a web browser.
Strange that they went the copyright way, though. IANAL, but isn't accessing a service you've been explicitly forbidden to (via ToS or similar) a violation of the CFAA?
You are 100% wrong. The ad copy on craigslist IS copyright protected so it doesn't matter where you scraped it from. TOSs do govern the data whether or not you are viewing a cached copy or not. By your logic all TOSs are rendered useless if you browse the net via proxy servers.
You can scrape anything off the internet you like and do as you please...but you can't create a business out of it.
Site TOS don't really matter too much or else Google could never exist. They're mostly to limit the liability of the publisher and not to prevent anything with the accessor. Googlebot is not a lawyer, it can't decide the legal implications of scraping or what exact activity can be done with the data it finds.
Google also overlays facts it finds by crawling the web in maps (Google Places and the One Box results) and uses the creative contribution of other people to provide things like reviews inline on SERP. Google is a bad target to sue though because they will punch you right back in the face.
Strange that they went the copyright way, though. IANAL, but isn't accessing a service you've been explicitly forbidden to (via ToS or similar) a violation of the CFAA?