haha I confess, I myself had failed many times signing in some private accounts, because of this CAPTCHA security technology! Specially using my mobile, or when they are case sensitive while you don't know!!
CAPTCHA is made to avoid bots & inhuman tries to hack or enter private accounts, still I'm not a very big fan of it.
Well whether I like it or not, it is not a covered subject in Microstocks which inspired me to have these illustrations!