Google recently introduced a new API for its spam detecting reCAPTCHA - calling it the "No CAPTCHA reCAPTCHA" since it no longer requires users to figure out and type the distorted text they see.
In this great post by Bartosz Góralewicz, he lays out how using a bot to search google and not click on the target website can send negative CTR signals to the site...especially in light of all the