Thanks everyone for their input. Really helpful! I'm a little unconvinced but the statement "In general, if you're being attached by spam, using a captcha is a good idea...". It's not that clear cut - captchas have costs and benefits. It makes sense to at least start by trying the approaches that are invisible to the user (i.e. honey pots etc). If the spam problem still proves too great, then resort to captcha as a backup, rather than as a first response.
Interesting to see that in the sampa.com case study, Marcelo said their conversion rate went from about 10% to 10.9% conversion. (i.e. removing the captcha meant that almost one extra person per hundred completed the activity). This isn't insubstantial, but I'd expected it to be higher than that, since personally I always struggle with captchas. As Jeff said, the other thing to consider is that they aren't a uniform commodity, some are easier than others; while also user journeys can vary wildly. If a user spends 10 minutes signing up to a service that's highly important to them, a simple captcha isn't going to deter you much. But for a 3 second transient interaction (like a quick comment or thumbs up), a tricky captcha is going to feel inappropriately heavyweight. I'd really hoped to discover a large scale quant study on this... Anyone? Harry ---- www.90percentofeverything.com ________________________________________________________________ Welcome to the Interaction Design Association (IxDA)! To post to this list ....... [email protected] Unsubscribe ................ http://www.ixda.org/unsubscribe List Guidelines ............ http://www.ixda.org/guidelines List Help .................. http://www.ixda.org/help
