If you Google "recaptcha", the second suggested search-term expansion is "recaptcha cracked". This mainly leads to a fluffy article that pits one field expert's assertion that reCAPTCHA can be cracked, against Google's rebuttal that the crack demo is based on an outdated implementation of reCAPTCHA. This, dated January 2011, and some mid-year buzz from a handful of vBulletin operators saying they're suddenly getting a lot of successful spambot registrations through their reCAPTCHA wall - so either they were victims of man-in-the-middle compromises or there was a temporary surge of successful reCAPTCHA cracks that have since been ironed out.

I first checked out the beta-class "Cool PHP Captcha" Google Code offering, but within 5 trials I failed one (ambiguity between lowercase "n" and "h") and within 10 trials I encountered a borderline inappropriate challenge word: "tittery". This prompted a review of the challenge-term dictionary. Suffice it to say, "tittery" was not the most inappropriate word in the list. So rather than knock myself out reviewing the whole dictionary, developing my own dictionary, or evaluating more implementations, I'm just going to roll with reCAPTCHA.