[amitdugar]

If this gif CAPTCHA system becomes popular, there will be some smart hacker who will figure out a way to crack this (read first frame, match different frames etc.)

I wish there was some better CAPTCHA alternative. CAPTCHA can be really horrible sometimes.

I know some people who close a webpage when they see a CAPTCHA, unless they have no other option and are forced to fill the form.

[smcl]

You don't even need to be a particularly smart hacker. Even just dumping a screenshot of the page [1] using phantomjs gives you a relatively legible image.

[1] http://blog.mclemon.cz/apple-nucaptcha-easy-to-break

[amitdugar]

so apparently reCaptcha is more secure than this one.

From Nucaptcha's website : "...most secure and usable Captcha solution in the market." :D