They're bad enough for able-bodied users, and I can only imagine how annoying and discriminatory they are for users of assistive technologies. There really ought to be some sort of law to get rid of them, or at least significantly restrict their use.
Google does the same to block scrapping of search results.
Google, of all companies, should be capable of coming up with a better way to detect and prevent web scraping. Broadly-targeted CAPTCHAs are extremely lazy.