TOPIC: need reCaptcha

How can we integrate a reCaptcha (or at least *some* security mechanism) into the MailChimp signup form?

Yes, we are getting spam registrations.

How is it possible that you are getting spam registrations? When people subscribe, mailchimp sends them a mail. If they don't confirm (click the link in the mail) they won't end up in your mailchimp list. It's true that they might end on your cmc list, but it doesn't matter. They won't end up on your mailchimp list and thus won't cost you any money.

Regards,
Daniel