I think it really depends on the application of web scraping. (As someone who does, what is in my mind, ethical web scraping)
- Scraping public information from government websites to do analysis: ethical, it's the public's data
- Scraping to help some companies customers more effectively use that companies product, for example scraping a medical office's insurance claims to help them automate their insurance remittance process: ethical
- Scraping faces to build a surveillance-tech company: disgusting
- Scraping your own website because your internal processes are so broken you can't get it any other way: ethical
- Scraping to just copy someone's data they worked hard to generate to go and resell: unethical
- Scraping public information from government websites to do analysis: ethical, it's the public's data
- Scraping to help some companies customers more effectively use that companies product, for example scraping a medical office's insurance claims to help them automate their insurance remittance process: ethical
- Scraping faces to build a surveillance-tech company: disgusting
- Scraping your own website because your internal processes are so broken you can't get it any other way: ethical
- Scraping to just copy someone's data they worked hard to generate to go and resell: unethical