Preventing automated account creation

Hi, I have been investigating ways of preventing automated account creation on the e-commerce system I am currently working on. Obviously I have seen the graphical solutions to this problem, a small image containing several letters and numbers which must be typed in by the user to confirm account creation. However, this (it seems to me) is a bit overkill for what is a pretty small client, I'm not entirely sure it's a good use of time to create this script solely for them, does anyone know of anything pre-packaged? Furthermore is it really worth doing this, what risks do automated account creation present to an e-commerce site? Tom Williams, Digital Data