Big Egg Toys
It definitely works. I have been using clean talk for about 3 years via another CRM. it does it's job and yes the app on shopify only allows the user to input api key which may seem a bit intimidating for most. Regardless, if you are running a store having spam protection is critical to the safety of your store.
I installed this app because we had a regular spambot/hacker that was signing up to the newsletter 50x per week with real peoples email addresses. Both Mailchimp's recaptcha and Shopify's Google recaptcha did not do the trick. CleanTalk does! It was super easy to install, and the dashboard gives a great overview of what happened where. Yes, very satisfied, and will save me hours of manual deleting. (dont let the fact they do not have any other reviews here scare you away- in Wordpress they have many, many good reviews)