No CAPTCHA reCAPTCHA
How many times you feel affronted while reading those stupid numbers or words and re-entering it just to prove that you are a human. We call them CAPTCHA(Completely Automated Public Turing test to tell Computers and Humans Apart) and recommend it to avoid several kind of flooding attacks, brute force attacks and sometimes even for CSRF attacks.
It's time-consuming as well as frustrating.