Looks like you can see the Google catcha in action here:
https://www.google.com/accounts/DisplayUnlockCaptchaHitting refresh a few times shows that there are indeed some very hard to read ones and the audio is almost completely unintelligible to me, I certainly can't make out what I am supposed to type from the audio.
I'm glad I've never had one of those pop up in real life.
Maybe you could add something here:
http://www.google.com/support/forum/p/gmail/thread?tid=1362c6c8aa7ab5c4&hl=enfor all the good it will do, Google just don't do support