Sometimes I use one of these operators by mistake and get instantaneously hellbanned from using google. The first time the captchas kept reappearing a whole day. I read somewhere that the ban is resetted the next day, but the next day I was still getting the captchas and couldn't use google for anything.
I deleted all cookies and suddenly I wasn't banned anymore. So this looks to me like a captcha bug, or a chrome bug, or both. Probably both.