The opinion of one HN’er is that it is definitively a gray area. So whether or not you’re sued for it depends on if someone resourceful has a reason to sue you (e.g. LinkedIn vs HiQ); in most other cases, I don’t think anybody really cares.
There was an earlier case (I don’t recall the details) about scraping violating copyright, which might be a valid defense - that you’re engaged in unauthorized “copying” the (protected) source code (of the webpage), albeit momentarily, into your computer’s memory while your script processes it to extract the relevant contents. So even though it might be fine to copy the image/data/whatever else, you have no right to copy source code - which is certainly protected by copyright (your browser processing the same page is something the copyright owner explicitly allows, by virtue of making it available on the web). By that same token, it can also be considered illegal to save webpages on your harddisk. But do refer to the last sentence in my earlier paragraph.
The LinkedIn vs HiQ case is currently being appealed in the (court of appeals for the) 9th Circuit. Regardless of which way it rules, the decision of the 9th circuit only applies in its the states under its jurisdiction (maybe as a precedent in others, but it won’t be binding). It can still go to Supreme Court, depending on how determined the parties are.
There was a ruling in a different (but somewhat related case) in Jan 2018 that violating the ToS is not a crime https://www.eff.org/deeplinks/2018/01/ninth-circuit-doubles-... To quote: “[T]aking data using a method prohibited by the applicable terms of use”— i.e., scraping — “when the taking itself generally is permitted, does not violate” the state computer crime laws”.
There was a very long discussion on HN about scraping over a year back:
https://news.ycombinator.com/item?id=13884357