When things are already completely broken then it's acceptable to move fast because things are already completely broken. When things are only slightly broken you need to be careful you don't expand the breakage.

Are you sure CloudFlare isn't working on this right now? Captchas are very hard (if not impossible) to do right, and audio captchas are no exception. Check out http://uncaptcha.cs.umd.edu/ As far as I know CloudFlare might have a large team that's been working on this for a while but has been unable to create something solvable by a human but unsolvable by a bot.