We manage 100+ sites for different businesses. Every week one or two of our clients forward a similar email to me, asking of they should register. I explain the scam and they are happy. I'm sure lots of unsuspecting people buy extra domains from such scamers.
...and have the form require captcha of some sort
That will not work with this particular scam (but captchas are good for most). We heavily encrypt all email addresses on all sites we manage. The fact that our clients get these scam emails tells me this scam is manual not a bot thing.