There has been a few thread about that one, so we decided to add it. We just added a plugin that lets you use Google’s reCAPTCHA form to your app. That way, you can check if your users are actual people, and prevent robots from spamming your site and database.
The way it works is very similar to an input. After adding the plugin and entering the keys you’ll get from Google, you can draw the element on the page. When the user does the operation and is recognized as a human, the input’s checked status will be true. You can use this in a condition on workflow, etc.