This ticket is the suggestion to turn captchas into actually useful micro-edits, like the classic reCAPTCHA (http://en.wikipedia.org/wiki/ReCAPTCHA) did with scanned images. this could be a number of different things, image editing/cropping, OCR (commons to wikisource), or edits as currently developed by WikiGrok.
For example you could first show a Wikidata item without an "instance of" to a number of users and let them decide if it's a person or not. Then once some data has been gathered you could use the same question as a captcha and check against the previous answers you got.