One of the key notes of humane UI design is that the average user is terrible with the mouse. Joel Spolsky touches on this in one of his articles: http://www.j

One of the key notes of humane UI design is that the average user is terrible with the mouse. Joel Spolsky touches on this in one of his articles: http://www.joelonsoftware.com/uibook/chapters/fog0000000063.html http://www.joelonsoftware.com/uibook/chapters/fog0000000063.... Depending on the sensitivity, this CAPTCHA could definitely drive away users.