I just tried to register for the first time, and it took a number of tries to get a captcha that I could decipher--and I'm a human, I swear! The images only ever displayed the first letter of the string, and I had to take a number of cracks at the audio one before I got one that didn't have any ambiguous F/S Z/C sounds (or maybe that's just my crappy laptop speakers.
Is it supposed to be that hard, or is there a problem with the system?