Captcha

To prevent bots from registering for the site and adding spam, captchas are useful, so I know I'll have to add them to TreeTapper before allowing users to register. While signing up for the new Encyclopedia of Life site, I found they use the reCAPTCHA service. This uses scanned words from books as images for people to interpret (people receive a pair of words, one known and one unknown). Free captcha service, plus gets people to help digitize books -- sounds like something I'll use for TreeTapper.