As of WSN 10.1.7, reCAPTCHA will be enabled by default using shared keys with no domain restrictions. This will provide a better out of the box spam-prevention experience on new installations, avoiding the accessibility issues of WSN's internally-generated CAPTCHA.

You may still wish to replace the shared keys with your own keys in order to have control over the challenge level (more human-friendly or more secure against machines).

I've also added a line to the privacy policy page when reCAPTCHA is enabled which explains that it uses cookies and shares data with google, fulfilling EU privacy disclosure law.